First thing's first; how much should I raise preflop? Well, for the first 3 positions after the big blind, raise 4-5x the big blind. If it's a tight game try 4x, if it's a really loose game you might try 6x-7x the big blind or even call and hope for an opportunity to reraise. You don't want more than one or two callers with aces (two callers can be dangerous) for a few good reasons.
1) Aces are a hand that players will almost always take to the river, if not taking the pot down before-hand. If this hand commits you, then you want the best odds with such a commitment and that's heads-up (almost always 4:1 in your favor).
2) Unless you hit a set, you're opponents can only do better against you, and having more of them increases their odds of hitting a two pair or monster draw. What are you going to do when you throw out another large bet on a seemingly harmless flop and two players call you? Do you bet the turn again if a scary card comes off or do you check and possibly get bluffed or outplayed? These are decisions I'd rather not make, especially since your opponents can probably put you on one of several big hands if you raised big or reraised preflop and you might not be able to place them on a hand, particularly if they're loose.
3) More players in the pot means a bigger pot, which is harder for opponents to get away from. Even if you are a huge favorite on the flop, you may find opponents chasing and catching with low percentage draws, just because you have so much of their money in the pot already. Now, this is a good thing against one player, but against two players you may not be even a 40% favorite, especially if they have different draws i.e. straight draw vs. a flush draw
In mid-late position I will still reraise any raises in front of me significantly, but if there are no raises in front of me then I would consider 4-6x the big blind. The only callers I'd want in this situation are the small or big blind because they'll probably check to me on the flop giving me control where I can check if I think I might be beat or throw out a continuation bet to see where I'm at in the hand. If someone behind me calls then I might be in trouble because if I check the flop they're going to think I'm weak and bet it out. I can choose to check-raise them at that point, but if they call or reraise I know that I'm drawing thin if they have me beat, and even if I have them beat any card is a scare card because it might give them two pair, at the least.
In late position, raising and reraising makes a lot of sense with a wider range of hands, so you can cloak your strength here a lot better than in early or mid position. Because of this, don't worry about the bet size and you might consider acting a little crazy and betting 10x the big blind or reraising 7-8x the raise. Careful, though, because this will often pot-commit any callers and if they hit they're not going to bet friendly, so be willing to win or lose a lot of chips if you go that route.
In the small or big blind, if you have 5 or more callers already it's time to bet 10-20x the big blind or even move all-in if you are going to raise. The worst you can do is raise 5-6x the big blind and have everybody call you, so your objective in this position is to either take the pot down right there or isolate to one player with a humungous bet or, you can give up the excitement of raising with aces and call the small blind or check the big blind, hoping to flop or turn an ace and surprise your opponents, or even take down a pot where you think those involved are battling over top pair kickers.
If you want to become an excellent or pro poker player, then you need to understand why to NEVER MIN RAISE with pocket aces. This is the worst action you can do because it advertises a huge hand and gives everyone pot odds to call. I don't know how many times I've seen aces go down in flames and complain afterward when they gave their opponent(s) 3, 4, or even 5:1 odds to call them. If you're going to wave a flag that says, "Hey, I have aces," you might as well get most of the player's chips in the middle if they're going to take you on anyway.
Believe me, there are players at all levels that will call you even though they know they're beat. If not, you take down a pot preflop and there's nothing wrong with that.
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