I search a litle bit and I found this guys...
Middle Stages
"This is typically the stage where the antes kick in. How you play here will depend on how you did in the early stages, so we'll separate this into three categories:
SHORT (< 20x the BB) - basically, you're going to have to look for two types of pots. 1) Ones where you can double up with premium
hands (and you should push these hands aggressively) and 2) Ones where you can pick up pots with minimal risk despite holding marginal/poor cards (some good examples - being on the button with two players you know are very tight in the blinds or my personal favorite, moving all in from late position, or the blinds when two weak/passive players have limped in, these are easy stack builders).
MEDIUM (20-40x the BB) - here it's important to play positionally strong poker. Don't be raising with pocket 2's under the gun (but at the same time if you think you can limp in with it and see a cheap flop, by all means do so) and don't be calling raises with K-J. Use first in vigorish to your maximum advantage. Re-raise positional raises if you feel they are just that. Don't play overly tight, but pick the right spots to make your "gap" steals.
BIG (>40x the BB) - you still want to play positionally strong poker, but you can afford to take a few more luxuries. Where you might have limped with pocket 2's under the gun with a medium stack, with a big stack you can raise. You have the chips to induce fear - use them. You should be applying the gap concept liberally, open raising at least 1-2 times an orbit. This will pay off when they eventually 1) play back at you when you have a hand or 2) just call you and you hit the flop with your marginal hand and they pay you off."