Plrs/flop and average pot are a really good indicator if a fish is in a table. Generally, tables with more than 30% plrs/flop are good tables and have 1 or 2 fishes.
Some other things you need to know:
-Try not to have a good or an aggresive player on your left. Midstackers regs are also annoying having them on your left. Having nits on your left is great since you can steal really wide and not get punished.
-Try to be in position on the fish. Being in position on the fish is a lot more important than having position on any reg.
-Start tables yourself, since fishes don't like waiting and they just join any table they find. When you are starting a table, make sure you join a seat on the top left of the table. Most players that join a table generally sit on the bottom right or on the central seat.
-Always mark the fishes, the regs and the nits (with the pokerstars system, not hm or pt) so that you can track them more easily when you are going to join any table.
-Make sure you check the lobby regularly so that if a good table is available, you can join it immediately.
-Imo, don't join waiting lists. Unless there is a crazy donator on a table, there is no point in joining a waiting list.