Here is a sample of something I have adjusted recently with good results. I have talked alot about middle pair and a Pocket pair that makes second pair. Here is another good sample:
Full Tilt Poker Game MTT (early levels) No Limit Hold'em
columbo posts the small blind of 25
phenzor posts the big blind of 50
MP calls 50
BUTTON cedricus78 folds
Dealt to columbo [9c 8d] in SB
columbo calls 25
*** FLOP *** [4h Kc 9d]
Now in this spot, it does not matter if I have A9, or TT. They are both a dog to the King, right? Okay. Now "ABC" poker for beginners tells you to bet out here to "see where you are at". I now know this to be a terrible play.
It does not meet the basic criteria of "why we bet". I am never going to get a Paired King to fold there, nor would any hand worse than middle pair call. I am better off checking and seeing who makes a play for the pot. If someone shows up with a King, ok I was beat already. (If someone stone bluffs there in early levels, more power to him as its -EV.)
But if the middle pair IS good, then I keep the pot smaller (giving less incentive to bluff) allowing me to call a bet and float to the turn. I may even be able to get a King with a lousy kicker to fold on a later street which will not fold on the flop.
But best of all, if I am wrong, I lose out on a small pot. That's it. If an bluff card comes on the turn, I may get to use it since I have not sent a message that I had something already on the board/ (not that I recommend this play, just thinking out loud) I dont want a big pot to form here with nines or tens. They have SHOWDOWN value in a small pot, but will easily get blown out of the hand if a big bet comes.
The other big change I understand much more is that of stealing with 89 or 75s vs. KJ. When I get a steal CALL and I have KJ, I will never know where I am in the hand. If I get played back at with 89, I can just dump it pre-flop or post flop if I miss. And if I hit, I can win a bigger pot with a disguised hand. The hard part is raising with these hands in the middle levels.
The third is understanding when you have fewer than 60 Big Blinds, there is no chip utility. Therefore when you have the best hand, RAISE. check-raise is especially nice. But we are NOT going to big pots with marginal hands. I need to utilize pressure when I have those marginal leads to avoid showdowns.
These adjustments to my game have been huge.