github or git?  In any case, have you tried setting up a local and a remote on your local system to try out the commands without the fear of ruining your working repo?  You can set up a local and remote on your local computer, and push and pull from them in the same way you do with your local repo and github.  Example:

mkdir test

cd test

git init local_repo

cd local_repo

... add files, commit, etc.

cd ../test
git clone --bare local_repo/ remote_repo

cd ../local_repo

git remote add origin ../remote_repo

... add more changes and commit

git push origin master

Note, to be able to push, that repo needs to be bare.  You can also add a dummy linux user to your local system to play the role of a contributor.

Using this kind of setup really helped me understand git better.

Alren