Download Miracle Grue
Hack at Miracle Grue. Build the thing you love.
Write unit tests for your new feature or behavior. These tests need to have about 50% code coverage, and they must demonstate some kind of 'before/after' STL to show what features it add (or a fail cause, to show what bug you are fixing)
Send us a pull request. Wait
Maybe wait some more? Apologize, we are few developers and very busy, it may take some time to sort out your pull, and add it to our codebase.
Share! Enjoy! Post it, tweet your addition, and share the awesome contribution you have made to the whole community!