First find an open source project that you want to contribute to. Next find it's issue/bug tracker. Find an issue that you can reproduce relatively easily. Next

First find an open source project that you want to contribute to. Next find it's issue/bug tracker. Find an issue that you can reproduce relatively easily. Next get the source code and start tinkering around till you try and figure out why the issue happens. Next try and fix the issue and if necessary add tests. Create a patch and submit! Even if you can't solve the issue, just reproducing it and reporting your findings can be very helpful! Also make sure you read any contribution guidelines for the project if available. You will also need version control-fu, whether it's Git, Mercurial or SVN or whatever the project is using. You need to be able to use it, at least the basics to make a patch. Most importantly have fun and be nice! :)