[compay]

Whatever it is, start small. Smaller patches can be very useful and are also more likely to give you the satisfaction of being accepted. Even just correcting typos or grammar in a README can be useful as long as you're not a jerk about how you submit it to the original author. :-)

Github definitely makes contributing to open source very easy, so I'd recommend you start looking there. They also have some well-written practical guides to working with Git here:

http://github.com/guides