On the TA note - I was in a very different situation. My school only does undergrad, and those of us who TA are often grading our friend's papers. If not our friends, then people we know very well. Don't come bitch to us about your grade. Bring it to the prof, who would bring it to us. It's not (usually) our fault you suck...

I refused to do grading work unless it was a one word answer, and even then I'd ask the proff a lot about what he'd accept because grading peers is icky. We were selected carefully to be TAs since we know your grades and often other personal things from the professors about you guys so the proffs have lots of trust in us. We can't suck too much.

Oh yeah, on that note, go to the study sessions. I always brought my old tests with me and showed what I did (if not using the exact same test) and what I did wrong. If I did well enough in the class to be a TA, you might occasionally want to listen...