Debian / Ubuntu | sudo apt-get install git |
Fedora | sudo yum install git-core |
Windows | Download and install msysGit |
OS X | Use the git-osx-installer |
See the git page for the most recent information.
Have a look at the github install help pages available from github help
There are good instructions here: http://book.git-scm.com/2_installing_git.html