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2) Middle levels, don't limp unless you are trying to trap with AA.

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Two things to note here.

1) Unless it is folded to you in the small blind and you expect BB to raise you if you complete, NEVER try to trap with AA, this will only get you into trouble. You never want more than one opponent preflop with AA since there is a much greater chance your Aces will get cracked with more than one opponent.

2) In the middle levels, limping isn't a bad idea with mid pocket pairs if you're playing them for set value. Flopping a set has huge implied odds, and limping gives you the opportunity to check/fold if you miss your set.

MisterW