I look for tables that 45-50% of the players see the flop, but if the average pot size is too big relative to the blinds I either find another table or I just watch for awhile to see why the pots are so large. Too much raising is dangerous to your bank roll. If I sit down at a table with lots of raising I make sure I buy in with more then my normal amount e.g. a .25-.50 limit table with an average pot size of $6 and 40% seeing the flop tells
me there at least two or three aggressive players raising and re-raising, so if I played I would buy in with $20 rather then my normal $10.