Does anyone have any good information on joining a powerlifting federation?

I picked a federation based on location of meets- really important for cost effectiveness for a beginner. Different federations have different rules, so make sure you know your federation's rules prior to your meet- what kind of gear is allowed, pauses during lifts, timing, etc.
As for the first meet, set your openers at a comfortable level, because you don't want to bomb out! You should be able to triple your opener in the gym. And bring plenty of food!

I compete in USPA, and usually compete raw or classic raw (knee wraps). I currently hold about 16 state records (WV) and two American submaster records (bench and total, classic raw, in the 67.5kg class), and I'm currently nationally ranked in both bench and total across all federations.

I compete in two. I joined them based on meet proximity to me. I'm partial to USPA since I can compete in the submasters division (USAPL doesn't have a submasters), but I also joined USAPL since they've got a meet in my town that I want to do later this Spring. If you have a lot of federations in your area, why not go to a few meets and see which ones you enjoy more. I've heard that SPF ones (at least in Alabama) are pretty fun, and they usually run a deal around Christmas to sign up for lifetime membership which would save a ton of money. Other reasons to compete are that some have different rules for equipment, uniforms, etc., and even the actual lifting (monolift vs. walk out for the squat, etc.). Then there's also the distinction of drug tested or not. USAPL is completely clean. SPF has a reputation of allowing it. While you may be clean, do you care if your competitors are?

Really though, it's a crap shoot. It doesn't matter much (IMO) until you get to the point of setting national records.