[fundamental]

If you don't have a target project of your own in mind, but are interested in exploring a given domain open source contributions are one way to go. It let's you exploit the fact that someone already has built something cool and you're just adding to it or otherwise modifying it.

Programming is like other hobbies/crafts in that observing what others do and how they've done something will teach you about how you can better approach problems. There certainly is a barrier to entry, but if you've already taken some university level classes you likely have the basics down. There's social conventions to collaborating, but that shouldn't be a huge blocker. In my opinion, contributing to different organization should let you sample different project domains and either help you decide where to stick around or what types of personal projects might interest you.