The majority of this list came from http://cheat.errtheblog.com/s/git but I have added in some tidbits that I have found in other places as well.
git config -e [--global]
edit the .git/config [or ~/.gitconfig] file in your $EDITOR
git config --global user.name 'John Doe'
git config --global user.email email@example.com
sets your name and email for commit messages
git config branch.autosetupmerge true
tells git-branch and git-checkout to setup new branches so that git-pull(1)