wow. lots of misinformation in the backlog here.
a) if you want to block ads, use the adblock firefox extension.
b) privoxy or polipo are both fine. polipo will make your browsing feel a bit faster.
c) use torbutton, and then you don't have to wonder about java, flash, etc.
d) alas, don't read the wikipedia page on tor. nobody who knows much about tor has had a hand in it.