Git

The Drupal community thrives on being a "do-ocracy": if you encounter a problem with some aspect of Drupal - a module, a theme, or Drupal core itself, for example - you can, and should, try to fix the problem yourself.

This tutorial shows you how to install the Git version control system on a Mac. It assumes a little familiarity with the Command Line. If you don't know how to use the Command Line, then check out Addison Berry's excellent series of video tutorials over at lullabot.com: you can find the first one here and the rest here.