Advice on what to check in to version control...

I know this is slightly off-topic, but I always benefit from hearing others' opinions about workflow.  I work alone, basically, but move between machines and environments.  My workflow with other languages that don't have dedicated IDEs (R, python, perl, etc) have a clear division between what to check in and what not.  The .idea files and to a certain extent external libraries are workspace-related and I would love to check them in.  However, I have found it easy to get this type of thing wrong and end up with broken modules and projects as I move between multiple OS environments.  Any suggestions on how to keep things straight, or do I really need to spend the time to get Ivy/ant up and running for my projects?

Thanks,
Sean