I've been reading some posts regarding pot odds and EV; I still don't completely understand EV.

I think I am starting to get it, though.

So if the pot is 20$ and I have to call a $10 bet, my pot odds would be 1/3 ($10/$30), correct? Therefore if my chance of hitting my out is greater than 33% it is a EV+ play, correct? Or am I totally missing the boat?

Also, are there other considerations for calculating EV? I've been reading the strategy section also, and I can't seem to stumble on much about it. If there's a post explaining EV somewhere in there I'll read that if someone can post a link etc. I seem to see a lot of posts saying basically "Don't make -EV plays" etc, but I've had a hard time finding a post explaining it.

Again sorry for posting something that has probably been covered 100 times.