To get started with Android/AOGP, you'll need to get familiar with Git and Repo.
To initialize your local repository using the AOGP trees, use a command like this:
repo init -u git://github.com/AOGP-L/android.git -b lp5.0
Then to sync up:
repo sync
To Build AOGP ROM
$ . build/envsetup.sh && brunch <device>