It depends on how marginal their hand is. If they're overvaluing top pair type of hands, make better than top pair and get it in. Hopefully you can b/3b the flop all in.

If they're overvaluing draws, then you can pot flop/turn to exploit that. Unless they're trying to get it in with something like gutshot + two overcards which is marginal as hell since overcards are not always outs. But if they play their draws aggressively, it is actually very hard to exploit that other than calling when you have a good hand.

People that float too much with utter crap to try and take it on a later street should just be barreled off.