I set farm with middle/low PP at 10NL fullring. As described by Ahiltz, the basic formula is limping or calling raises as long as the opponent(s) have a stack that is 15*(the amount I have to call). This assumes every time you hit the set you will double up off the opponent, which generally holds true at the fishy tables. Short of that you fold the flop unless you have an overpair, in which case you should probably play it.