Hadley Wickham provides advice on developing R packages based on his experience creating over 20 packages. He discusses getting started with package development by choosing a name, creating directories, and adding documentation. Wickham also covers iterative development, testing packages with devtools, documenting functions and packages, and releasing packages on CRAN. He recommends learning from the source code of established packages and continuing to improve testing, namespaces, code style, and use of Git.