I can think of 4 reasons to just call a raise preflop with aces/kings/queens.

The first reason is to induce others to join the pot behind you. This may be smart if the raiser is short stacked and you're really not interested in isolating a short stack instead of trying to win a bigger pot from someone else. I used this very play last night in a tournament. A really short stack went all-in for $300 when the big blind was $50. I was in the cutoff and was a short-stack myself with about $800 chips. I decided to just call in order to induce others behind me to come in and double me up. It worked out perfectly when the button called and then the big blind pushed all-in. The big blind had nines and was apparently trying to isolate the short-stack while getting some dead money in the hand (trying to get button and I to fold). The button dropped and I ended up with a lot more chips than if I had isolated the short-stack myself. If this was later in the tournament, I may have gone ahead and isolated, but I was willing to take the risk and bring others in the pot in order to get some chips early in the tournament.

The second reason is to attempt to trap a big stack by surprising them. If you just call, then it is hard for your opponent to drop TPTK on the flop. This is heavily based on the type of opponent the big stack is. If he is tight/passive, you may just want to put more money in preflop to increase his pot odds to follow along for the ride after the flop. If he is loose/aggressive, this works beautifully because they may think that you're just not giving them credit for a hand and pay you off post-flop.

A third reason is to pot commit a medium stack. If they put 10-20% of their stack in preflop and think that they'll put in another 20-30% on the flop no matter what, then by the time you raise them, they'll already have half their chips in the middle and may go down with whatever hand they hold, no matter how thin they're drawing. Again, this is most effective when you think they will take a shot at the pot even if they miss.

The last reason I can think of is to avoid a big all-in if possible. For example, you make the final table of a big tournament as the second biggest stack by far. The big stack at your table has a tight image and raises from early position. You have queens, but you may not be interested in an all-in hand unless you are positive you have the best hand. There is too much tournament equity on the line for you to run into AK, AA or KK. You could raise here and fold to resistance, but you could also just call hoping to see undercards or a queen. With undercards, you can show strength and then decide if you want to fold to resistance. A tight opponent probably won't want to tangle with you either since you can do the most damage to him/her when there is real money to be had at the final table.

I love making tricky moves like this, but be careful. You can't get angry if they were stealing with 42o and the flop is 442 and you lose your stack. My basic premise for when to slowplay a big pair is the size of the pot and my opponent's stack compared to my stack. If I'm short stacked early in a tournament, I am more willing to take more chances trying to double or triple up. Late in tournaments when the blinds and antes are significant, then just winning them plus the raise can make me happy enough to just go all-in and avoid even a 70/30 KK vs. AJ situation for all of my chips. I haven't yet used this play late in a tournament and don't foresee this either.

As far as ring games, I don't like to slowplay big pairs preflop unless I'm playing against a certified maniac. Loose players will give me action on my strength and tight players will only call your big river bet if in fact they have rivered you, so there is no use in slow playing big pairs in that case. The best you can hope for is for them to flop a set or two pair at the same time you flop a set....unlikely. I'd rather them call a big bet preflop and then be forced to call another big bet post flop when they get a draw or TPTK. That is just me. There is nothing I love more than people slowplaying aces and kings against me. At the 200NL table last night, I was in the big blind and the button called. The small blind just completed with aces. He checked the flop, which had given me 15 outs. I checked (don't know why) and the button checked. The turn missed me but he gave me a free card to hit the nuts. He was the kind of player that could release a big hand if he thought he was beat, but he ended up winning a small pot while risking losing a medium pot.

Warning: If you have a read on a loose opponent and want him to keep playing aggressive, DO NOT slowplay. Being an occasional aggressive player myself (wink), I try to discern between tight/passive opponents and tight/tricky opponents. If you slowplay aces or kings against me, I will put you into the tight/tricky category and change my strategy against you quite considerably. I will bluff a lot less knowing you're trying to induce them and I will begin setting up traps against you, becoming more tricky myself. If you have a read on your opponent, don't do something to change the way they're playing and don't confuse them. The trick to outplaying your opponent is to get them thinking opposite of what you're doing, not confusing the heck out of them. If they're confused they may make the right decision for the wrong reason and then you're screwed anyway.

Check out doubleas's book, Pressure Poker: Poker Strategy and Tools to Improve Your Game (also available in the PokerSavvy Shop)