On FTP, I filter for tables with >30% players per flop, and I browse to find a seat with two big stacks on my right and two small stacks on my left. I immediately look up the two players to my left on pokertableratings to see whether they are winning shortstackers and how tight/loose they play (good full stack regs usually keep their stacks full, so in general the guys to my left are either bad players who lost part of their stack and do not top up or shortstackers, lots of which (but not all of them) are also bad players).

Doesn't mean I always leave if the situation changes, but I certainly tend to leave when good players sit on my left full stacked, unless the table is otherwise juicy. I also tend to leave when the whole table starts playing super-nitty.