Basically you just need to add lines to ~/.gitconfig
[alias]
st = status
ci = commit -v
Or you can use the git config alias command:
$ git config --global alias.st status
On unix, use single quotes if the alias has a space:
$ git config --global alias.ci 'commit -v'
On windows, use double quotes if the alias has a space or a command line argument:
c:\dev> git config --global alias.ci "commit -v"
The alias command even accepts functions as parameters. Take a look at aliases.