I second stingers opinion regarding the Aircraft callsigns. Knowing the aircraft characteristics well is also helpful and obviously the airport layout. Aside from that, I wouldn't get to worried about learning phraseology. It's actually pretty easy and most people, regardless of aviation background, seem to have a good grasp on it after just a few days. I know the pass rates are alarming, but the things that trip people up on PA's are more technical situations that you aren't going to be able to really prepare for until you're actually doing it. Not to mention if you think you're doing it right and are practicing without an instructor there to correct you, you may develop bad habits