[indiefan]

Find a project you're actually interested in (not just interested in the notoriety of being a part of). The ide/environment kind of depends on the project and the language/assets that you'll be working with specifically.

Once you find a project you're interested in, find them on irc. Don't be too pushy, hang out and try to pick up on the dynamic. That doesn't mean you should be silent, just don't be annoying.

A great way to catch up on an existing project (the earlier you get on board btw, the easier it will be to start) is to start helping out with testing. A lot of programmers don't enjoy writing automated tests (which they should be writing first anyways), so that stuff usually gets left to someone to clean up. An ancillary benefit of which is that you can learn a ton about a project by adding tests.

The only other thing you'll probably need some experience with kind of across the board is version control. Experiment a little with git/svn so that you aren't intimidated by submitting patches (version control can seem intimidating before you've worked with it, but most of the time it's pretty basic).