There are some old posts in the beginners section about table selection from fnord and company i think which are worth looking up.
i find that i can outplay players at 50nl post flop therefore i look for quite passive tables with small pots that i can dominate easily. I try to annoy the table with lots of large raises with marginal hands so then i can tighten up when they get annoyed and wait for the monster. I found that at highly aggresive tables or tables where pots get big it took too long for me to figure out when i was ahead and i lost money because of this so i choose this method instead.
I think though its contrary to what alot of players like to do.