make notes about them........
You will find that you will play these guys a lot and if you know that they slowplay monsters you can be aware of it and make a judgement call.
But don't fall into the trap of slowplaying your AA, by going 1BB you invite a lot of people to look at the flop and find that you lose to trips, flushes and straights that wouldn't have stayed in if you had been aggressive from the start.
Your best move against slowplay is having the best hand 
Read the articles on this site, use the starting hand charts and be aggressive preflop and look at other people's position -
example
Imagine you are Button with AQ. UTG opens with 1BB - I would presume Ax, low pair or suited but not connected - generally they are trying to limp into the hand so see if they can hit on the flop!
Against your aggression 4BB + 1BB (caller) most fold (not all). Someone slowplaying AA will call. But at least now you will have some info and you can be wary or aggressive depending how the flop affects your hand.
Let's say that Q72 rainbow flops - top pair, top kicker - a good hand and you have position, you can see what your opponent does.
He checks, you bet 3/4 of the pot (8BB) - if he calls he is either a maniac or has AA, KK, 77, 22 and is ahead or possibly AQ, KQ, QJ, QT.
You now have a decision........
Without notes on the opposition I would be concerned that I could be being slowplayed - if he checks again, you could check or use a smallish raise. On the river if he checks again I would probably just check. Then make short notes on my opponent for the future, slowplayed AA or maniac!!
