How do I start off getting involved in open source?

I am a mostly-self taught developer, trying to develop my skills and it seems quite clear that getting involved with open-source projects is probably the best way to go about doing that, but I am never really sure where to start. I have accounts on the major OSS hosting systems and have checked out the code for a few projects I like, but beyond that, I feel kind of lost. Most OSS projects appear to me to be either abandoned, barely maintained, or so complex that I'm never even sure where to start. Does anyone here have any pointers or advice for starting off with programming OSS?