The Serval Project uses Git to manage all software source code, with GitHub as the central source code repository. (GitHub is also used for tracking bugs.)
The official Git documentation includes the Git manual pages (reference) and an online Git book to help you get started. There are also videos, cheat sheets, and a pile of links to other Git tutorials and books.
help.github.com has lots of helpful information about Git and GitHub. If you are new to Git, the Git bootcamp section has great step-by-step instructions of how to get started.
Some developers find SmartGit to be a useful GUI based application for managing local Git repositories.
Eclipse has a plugin for GitHub. See the EGit User Guide for instructions.
Please contact one of our engineers for assistance using Git with the Serval Project. They are happy to help with specific problems, but will not provide general instruction that could be gleaned from any of the above resources.