I'm writing this for two reasons:
  1. To solidify my thinking a bit
  2. To save someone else who's new to NL cash play a mistake or two. Always better to learn from someone else's mistakes, though other people's experiences are never as strong as something learned directly.
I'm not Mister Guru Poker Guy or anything; I'm just a dude who's learned not to be a total donk all the time over the last couple of weeks. What follows is a list of some of the things I've learned that make me a bit less donk-like.

  • Play Money practice isn't. Playing for real money in ring games is different than playing for pretend. Losing 10,000 play money chips over some statistical aberration that paid off for the other guy hurts in a very different way than losing a real buy-in. A buy-in that came out of your bank account, or could have gone into your bank account, or that represented 3 hours of grinding work. It also leads to different play in the games themselves.
  • Top Pair/Top Kicker sucks. Top 2 pairs (very often) suck.Your AK hit an AK6 on the flop - great. If you think you've got the best hand and someone else matched their 66 holding, then you're about to lose your stack. That's poker -- accept the possibility and develop the discipline to lay down a hand when you know you're beat -- more often than not, you're right.
  • Overpairs suck. See above. I played a hand the other day where I was dealt QQ -- the pre-flop betting convinced me he had a bigger pair, but I called to take a look at the flop. The flop came Qxx and I took his stack -- this happens. If you've got AA and someone tells you you're beat by his betting, unless you've got a specific reason that this guy is bluffing, lay it down. Yeah, sometimes he might giggle, flash unsuited crap, and get away with it, but for me this has been a +EV move when I've followed this advice.
  • Trust your reads. About 20 minutes after that last QQ hand, I was dealt QQ on another table and suspected the guy had aces. I called telling myself I'd fold if I didn't hit my set. The flop came AQx, I convinced myself there was a good chance he had been raising with AK or KK, called his all-in, and lost my stack with queens-full to his aces-full. I should have trusted my read.
  • Trust your reads part two. Same day as above, I had AA on the button, raised strong, and the flop came 7x7. I raised post-flop, got reraised, made a comment about how I hated AA, and was shown 77 after I folded. The guy flopped four of a kind and my willingness to fold a big pair saved me a bit more than a buy-in.
  • Fold when you're beat. It doesn't matter how great your hand is -- if it's second best, then it's just gonna cost more money if you drag it out rather than folding when you know you're beaten. Learn from my AAA vs QQQ example -- flopping a big set is the opposite of great if you've got the #2 hand.
  • Manage your bankroll. There's plenty of advice here, but it can be summed up like this. You will have losing streaks, and if your bankroll isn't big enough (or you're playing stakes you're not funded for) then you will go bust eventually. If you manage your bankroll correctly you can reduce this risk to something like a 2% chance over your lifetime statistically, and going bust sucks. Be less greedy, and play with your head.
  • Implied odds matter, so start thinking about them.The example earlier is a good one, but here's another. My K3 in the BB hit a flop of KKx. UTG raised, button called, I called. Turn was the same, as was the river until the button reraised enough to put UTG and I all-in. It was out of nowhere, I had no read on the guy, the board wasn't at all frightening, and I didn't think he'd flopped a set (and he didn't have the pot odds to be calling along the whole time). Turns out his 96 offsuit made a well-hidden straight, and I bit. I'd call it bad play on his part, except he got 2 stacks as payback for his long-shot there. When you take away a guy's odds to draw to his hand, and he calls anyway and eventually hits his hand, DON'T PAY HIM OFF! If you know he'll play suited-anything, the flop brings two diamonds, and he keeps calling pot-sized bets until the river brings a third diamond and he bets big, then fold. Yeah, he could be bluffing, but odds are this time you're beat. Long-term he's making a money-losing mistake here, unless you pay him off that few % of the time he hits. You're trying to take money from him, not the other way around.
  • If you're just starting out, play tight. Follow something like AOKrongly's 19 hands strategy that's stickied here. It's not the most profitable way to play, but it'll let you learn for the minimum price possible. Playing "real" poker with a larger variety of holdings is a more profitable way to play, but it's also a great way to go broke unless you've developed the underlying skillset required to do so properly. Playing tight means you've got easier post-flop decisions; playing looser means you'll be in a number of hands with the second- or third-best hand, and knowing whether someone will fold to a bet, having good reads, knowing when you really aren't in a profitable situation, and all the rest are a vital part of that game. Those can be expensive lessons -- tighter is less expensive in the short run.
  • If you're not playing your best, do something else. The next hand is the next one you play -- if you're distracted, then do something else.
  • If you're playing great, even if you're losing, then keep playing. Poker's a long-term game, and your goal is to stack up a huge pile of correct decisions that will make you money in the long term. If you're on top of your game and bad beats keep coming, then comtinue the good play as long as you're not tilting. This assumes, of course, that it actually is bad beats you're seeing, and not bad play.
  • You're not all that good. You see that guy across the table from you that you think is so predictable? You're better than him, and if you wait for the right situation you can take his stack. See that other guy who's always playing and raising with random crap but only shows a hand that wins big? He's better than you, and you might want to avoid big pots with him unless you've got the nuts or damn close. If he's limping kings and re-re-raising with 96 offsuit, every one of his pots gets huge even if he's only got middle pair, he's consistently winning, and your head is spinning trying to figure out why, then you probably don't want to tangle with him. He's probably got a solid read on you and everyone else at the table, and he's setting up to take your stack. At the very least you'll have no confidence your (winning) hand is any good and you'll get bluffed quite a bit.
That's all I've got off the top of my head. Hope it helps someone.