This page does not necessarily need to contain a tutorial on how to use Git, as those have been done, but we should link to appropriate resources and provide at least a listing of commands you can use to fork your GitHub repository, push commits back to it, and merge changes from other forks.

For starters, here's the prototype documentation on drupal.org for using Git to maintain a Drupal module:

http://drupal.org/node/711070

http://progit.org/book/