Using git for the CS101 Contest:
If you don't have a GitHub login, get one and log in.
Fork the GitHub udacians/udacity repository.
It is located at: https://github.com/udacians/udacity
Point and click the "Fork" button.
Clone the fork to your local machine. Be sure to change directory to where you want to work.
git clone https://github.com/github_login_name/udacity.git
Substitute your GitHub login for github_login_name.
Taken from Github documentation:
(Changes the active directory in the prompt to the newly cloned "udacity" directory)
git remote add upstream https://github.com/udacians/udacity.git
(Assigns the original repo to a remote called "upstream")
git fetch upstream
(Pulls in changes not present in your local repository, without modifying your files.)
Create a new branch.
git branch your_branch_name
Substitute your desired branch name for your_branch_name.
Switch to your new branch.
git checkout your_branch_name
Make changes to the code.
When you're happy with the code:
git commit -m "I changed foo to bar..."
git commit -a
and enter the changes in the text editor that should pop up.
Push the changes back to your GitHub repository.
git push origin your_branch_name
You will now have a shiny new branch on GitHub. Then pushed the "Pull Request" button to let people know you've got code.