Price is normally calculated by the number of days. Usually, the more days you take, the less you pay per day. Cars are classified according to a class, small to large, prestige and specialty vehicles, and there is a sliding scale of prices for each car class. When you book you are usually given an example of a car type in that class, but it need not be that type you are receiving.

Rental car companies normally permit a small amount of time, usually around an hour, for late returns. After that, they can charge up to another full day rental for a late return. If you know you are going to exceed the rental period you can often call the rental company and arrange an extension. Normally the standard contract rate (without discounts) would apply.

Most rental companies have a one-day minimum rental period. Price for durations less than a day normally are not regulated. If you need to return the car at a significantly different time of the day, you can try haggling to get extra hours for free.

If the car is damaged or stolen, your liabilities (to the rental agency and/or others) can go far beyond the fee you agree to pay for the rental. In addition to paying for any repairs required, the rental car company will charge you for any loss of revenue while the car is being repaired, and administration costs for managing the repair. If your car damages another or injures someone, there are additionally the liabilities to this party, and possibly charges.

Usually, when you come to rent a car you are presented with several insurance options. Some of these are

• Collision Damage Waiver – sometimes included in the rental cost (but more often sold at high markups with aggressive upselling), this reduces your liability in case of an accident to a fixed amount advised by the rental agency.
• Theft Liability Waiver
• Windscreen Breakage Insurance – sometimes a small extra daily fee will cover you against the cost of windscreen damage
• Excess Reduction/Super-CDW – reduces the deductible amount in case of an accident to a lower or sometimes eliminates all liability. Can be a substantial cost on top of the base price amount.
• Third party insurance
• Personal Effects Insurance – covers loss of personal items in the car when it is stolen or damaged.

You should take the time to consider the insurances offered, how they affect your liability, their cost, and whether your personal car insurance, travel insurance or charge card (used to rent the car) provides partial or full coverage. Sometimes some of these insurances and surcharges are compulsory, e.g., in foreign countries where your personal insurance doesn't offer coverage. Sometimes some coverages are built into the base rate.

If insurance or waivers are optional, consider the following before accepting the charge:

1. As above, if you have an automobile insurance policy on your vehicle at home, check to see if it includes coverage for rental car damage at your destination. Some policies include this coverage only for certain locations, which is unhelpful if you're travelling to another country.
2. If you plan to pay with your credit card, check also to see if it includes rental car coverage. Be aware that in many cases this coverage is secondary (meaning your existing auto insurance coverage pays first).
3. If you have purchased a travel insurance policy that covers trip cancellation, medical expenses, etc., check to see if it includes a rental car collision/loss benefit. Some packages do, providing primary coverage up to a certain amount. (Primary coverage means that the insurance pays before other policies, including your own auto insurance.) Depending on the amount of insurance you buy, the per-day charge for a travel insurance policy that includes rental car coverage can work out to less than the per-day amount of a waiver. It is usually cheaper to purchase travel insurance than to pay for the Excess Reduction/Super-CDW at the rental counter.

Rental companies tend to prefer bona fide visitors rather than local renters when it comes to excess levels and excess reduction. Sometimes these are lower for international visitors booked in advance, for airport renters with a flight number, or for people using a corporate discount code.

Many of the insurances are void if you use the car in a manner not permitted by the contract. You are almost never covered if driving under the influence of alcohol or drugs, but some contracts will also not cover you if you are driving outside of the areas or countries permitted, driving above the snow line, using ferries or driving off-road. Read the fine print.

Some rental agreements may have a limit on how far you can travel per day or in total and will charge for additional distance travelled. Others have unlimited mileage. In either case, a photo of the odometer shot at the beginning and end of the hire is a useful precaution.

Even with unlimited miles, you may see limits that confine you to adjacent states or regions. Some hire car firms may even use satellite navigation receivers to snoop on motorists, and inflict a costly per-km or per-mile charge onto the entire rental as soon as one visits even a single nearby out-of-province point (like Ottawa from Gatineau). Getting those limits relaxed may involve added fees; violating them may generate stiff penalties...all in the rental contract.

Rental car companies are notorious for finding additional surcharges, sometimes not added until the point of sale. These can include location or airport taxes, improvement fees and other surcharges, admin surcharges, registration recovery surcharges and other local taxes. Sometimes local taxes are not just the local sales taxes, but also local vehicle taxes that are "recovered". At the Las Vegas airport, such fees can increase the cost of a rental by close to 60 per cent.

This practice has become so notorious that some consolidators promote themselves on the basis they guarantee to offer a fully inclusive price but check the fine print.

Depending on the jurisdiction some of these surcharges may or may not be actually illegal, but some rental companies just calculate that most customers don't know their rights and won't press charges for "a couple of bucks". One example are taxes: While it is perfectly legal to quote a price without sales tax in the US, sales tax has to be included in every price told to consumers in all EU countries.

If you work for a large corporation, you may be eligible for the corporate (employee) rate when renting a car with some of the larger rental companies in any worldwide location. Extra benefits may also include a reduced excess. Check with your company for a discount code that may apply. However, if you use an employee discount code, don't assume it will always result in a lower cost. Many employee discount codes have a cheaper rental rate and included liability, but have increased charges for mileage and one-way fees. Check the cost, with and without the "discount".

Similarly, members of professional societies, alumni societies, or even travellers with a partner airline can access discount codes. If you don't have travel insurance a discount code that lowers the excess (deductible) to a moderate amount can be worth a significant part of the rental cost.

Sometimes - though not necessarily always or even in the majority of cases - there is a (small) discount for buying the rental car, the hotel and the flight "in a bundle". Check carefully whether this is actually the case, as especially low-cost airlines are notorious for making money off of "commission" they get for selling overpriced hotel rooms and rental cars.

You need to choose a car to meet your needs.

• If you can't drive a manual (stick-shift), check that your car will be automatic. In the United States, rental cars are automatic by default, but in Europe they are usually manual unless you specifically request otherwise at booking.
• Check whether there is room for all the passengers and luggage you will be carrying. The car may not be the exact model you booked, and the boot (trunk) space may vary.
• If you are travelling on unsurfaced/gravel roads you may want to consider a car with high road clearance or 4-wheel drive. Some hire car agencies refuse to allow their cars to be taken on gravel or logging roads, or provide no roadside assistance if the motorist is stranded at some remote point on a road like the Trans-Labrador Highway, or increase the insurance excess.

You can usually hire a GPS with the car. Having a GPS when driving in a new city can save a considerable amount of time until you get your bearings. Check the price carefully, as GPS rental for a week can sometimes cost as much as a new GPS. If you own a GPS device or smartphone that works at your destination, the small comfort of a pre-installed GPS may not be worth the extra money.

Rental car companies often rent child seats or booster seats. If you are flying with a young child, sometimes you can take your seat on the plane to save the cost of this hire. Make sure the seat you have will attach to the car you are hiring and complies with the relevant standards.

If you are considering driving to a different country from that where you have rented your car, ensure that it is allowed and that the insurance will also cover this. Even in places such as the European Union where many countries have open borders with each other, each car rental company can have different policy coverage, and may differ between directions (e.g. you can take a Polish rental car to Germany but not the other way round). Sometimes this can be waived by paying extra. Shop around if your trip contains more than one country.

In some case, there are also restrictions on driving across domestic borders; for instance, most car rental companies in Australia prohibit taking their cars across the state borders with the Northern Territory and Western Australia, or onto ferries. Similarly, standard hire cars must not be used for driving in the interior of Iceland.

There are sometimes exclusions for ferries, unpaved roads and other special cases. Regardless of whether using the car off ordinary roads is permitted, your insurance may not cover such situations. The insurance may be void there even if damage or a breakdown isn't your fault. Read the fine print carefully.

It is common to restrict rentals to only drivers over the age of 21, and to apply a surcharge on drivers under 25.

Some companies insist that your license has been valid for a period of time. Provisional licenses can be problematic, and learners permits are always forbidden. Obviously, your license has to be valid in the country of destination. While this may not be a problem in most countries, other countries, most notably mainland China, don't accept any foreign licenses not even those from Hong Kong. Generally, it is a good idea to get an International Driving Permit (license) in the country your license is issued in before travelling. You may not need it in some countries, for example, USA and Canada generally recognize European driving licenses and Australia will recognize foreign licenses if they are in English. But for a small price it is best to be safe and prepared.

Some rental car companies offer an option to deliver a car to your initial hotel, and/or to pick it up in the hotel at your final destination. This option may be offered free as part of an extended period of rent (e.g. 1 week and more, as for Budget in Portugal). In this case, an agent comes with a full set of papers, everything is filled out on spot and you may not need to visit a rental office at all. Other rental car companies may pick you up in the car, and take you back to the rental car agency to fill out the paperwork. This is mainly so their driver has a way to get back to the rental car office, rather than being left stranded at a hotel without a car.

If your hotel has only paid parking around it, it is your responsibility to pay for parking time required for an agent to prepare papers with you.

Rental companies invariably require a mechanism to have a security deposit in case of damage, fines or even failure to return a car.

Many operators require that they have a true credit card that they can make charges against, often rejecting debit cards that can have the money withdrawn from them. Usually, a hold will be placed on a credit card for a security deposit amount. However, in many cases, they mean a card with protruding card details text, i.e. number, expiration, cardholder's name (cards like Visa Classic or Mastercard)--as opposed to Visa Electron or Cirrus/Maestro.

Renting with cash only is unusual, and you should check with the rental company that it is acceptable. If permitted it involves paying an amount of cash as a deposit roughly equal to your maximum liability which can be many times the cost of the rental. Some rental companies will accept payment for the rental in cash, as long as there is credit card available for the security deposit.

The security deposit amount held is not usually fixed in your contract and the funds may remain tied up for weeks (or a couple of months) after you return the vehicle. If having part of your credit card limit held may impact some other part of your holiday plans, you should check with the rental agency.

Before you go, check the exterior and front glass of the car and ask personnel to mark in the contract every scratch and dent you find, and sign the scheme on both copies of your contract, or even keep digital photos of the condition of the car and picture any damages at time of pick up and at time of drop off. When you return the car, it will be checked against the scheme you put in the contract. You can save considerable hassles at the end of the rental by just taking the time to note every scratch and dent.

Electronic tolling in many countries means that the car rental company will usually offer some kind of tolling service where they will make arrangements to pay your toll or provide you with an electronic tag in return for an administrative fee.

Some rental providers will charge a fee for every day of the rental as soon as you pay a single toll on any day of the rental.

You need to give consideration to toll roads on your route and whether they are tag, license plate or cash. You can then work out if it is cheaper to pay the local tolling authority directly, or if the convenience is worth the fee charged by the rental company.

Normally, a rental car is expected to be returned with the same fuel level as when rented.

• If the tank is not full when the car is returned but it was when it was received, you may be charged a premium - up to three times the cost of the fuel - for the tank to be filled.
• If the fuel indicator indicates less than full, do not leave without a rental agent noting it.

Some agreements offer you purchase of fuel at an attractive discounted rate. In this case make sure you are going to be driving enough to empty the tank, and that you can return it virtually empty. Many rental sites will charge you to fill the tank as though it is totally empty, not for the actual fuel needed to fill it.

Normally, the most economical approach is to agree to return the car full. Note that:

• Gas stations close to rental sites may charge considerably more - particularly airports and central city locations. You might refill large amounts elsewhere, and top-up at the end.
• Some rental sites may ask for a "fill-up receipt" as an indicator the tank has not been used much since being filled; you might just top-off the tank near their site.

You might get a car brand that you are not used to. Several car brands have a button or handle that must be operated in order to open the filling hole. It can be located on the dashboard, often between the steering wheel and the door, or on the floor at the driver's seat. Ask the rental clerk or check the manual if you cannot open the hatch.

The rental car agency will provide a number to contact in case of problems with the car. Make sure you contact this number first because they will usually have agreements with service organizations to fix or move the car. If you incur costs of towing, etc, without contacting them you may make yourself liable for the cost.

If you have a flat tire or similar, and the cost won't be covered by the rental car company, it may just be simpler to get the tire fixed than to arrange service through the rental car company, who may end up charging you more. However, if the repair will be covered by your travel insurance, you may want the rental company to arrange the repair so the paperwork is complete.

Automobile associations normally tie membership to individual drivers (not specific vehicles); this roadside assistance remains available when driving rented or borrowed vehicles. Reciprocal agreements often exist between automobile associations abroad, providing access to roadside assistance when travelling.

If you incur damage to the car the car rental company will initiate the standard process that they have for vehicle damage. They will identify the damage, and you will be required to fill in and sign an accident report form. If the office is unattended at the time you return the car, they will contact you and advise you to fill in the form and return it to them.

They will charge or place a hold on your credit card for the full amount of any excess that was defined in the rental agreement, even if that is obviously greater than the value of the damage. They will obtain quotes for the repair, and advise you the cost of the repair, and their administration cost. This process can take up to a month to complete. If this cost is greater than your excess, then that completes the process. The rental car company retains the excess. Otherwise, your card will then be refunded for the difference.

This is usually clearly explained in the documentation that the company will produce when you return a damaged car.

There is a risk that a dishonest rental car operator will attempt to bill you for minor, pre-existing damage to the vehicle which you did not cause; you may return a vehicle seemingly without incident, only to find that the dealer is claiming later to your card issuer that "hidden damage" was found later. Another potential scam involves greatly inflated repair cost - possibly from a repair shop owned by the same operator - or charges for repairs which were never made.

Very careful inspection of the condition of the vehicle both at the start and end of the rental, with the vendor present, is normally advised (don't be afraid to take photos of anything that might be disputed later) but is not fail-safe protection against fraud.

If you've obtained insurance outside of the rental agreement, they will usually require the final documentation from the rental car company before the claim will be finalized.