Aggression

It is proper in poker to play very aggressively.  Most good poker players will tell you that they're content to "go out betting" but they hate to call with the worst hand.  The reason is that as long as you are leading out with the betting you can win two ways - because they fold, or because they call and you show down the best hand.  When you call with a worse hand, you've simply made a very bad error in judgement (or perhaps gotten unlucky), but as long as you go out betting, you are putting the pressure on them, and you might have won with a fold.

For example, many aggressive No Limit hold'em players like to bet big (or go all-in) on the flop with a flush or straight draw.  The reason is that they have a 30-35% chance of winning vs. likely calling hands, and they also win if you fold.  If they also go all-in with their very good hands (good two pairs or better), it makes it a very hard situation for the caller.  The caller has to guess if you have just a draw or a big hand.  If you have a draw, they should call with any pair - in fact if they fold their pairs you are making a lot of money, because they're folding too often.  If you have a big hand, they need to fold those pairs.  Obviously you've put them in pain, and that's very good for you.

On the flip side, if you are up against someone who is playing this aggressively, you have to fight back very carefully.  For one thing, you need to also play back aggressively when you have position or a decent hand.  Another tool you can use is to raise preflop when you come in with good hands (and you only play good hands).  This forces them to also play good hands, so you can get a better read on their hole cards.  That way when they go all in or bet big, you can make a better guess of whether they are bluffing or value-betting.

It's crucial to make your opponents squirm; by betting big at them, you put the screws to them.  In No Limit or a Tournament, a lot of the game is psychological, and you want to intimidate and crush your enenmy.  You fire big shots at them, and even with pretty good hands like top pair, they can't call because they don't want to give up their whole stack.

You always want to have the "lead" in the hand.  The "lead" means you are the one doing the betting.  Most players will "check to the raiser"; this is generally very bad weak play by them, and you want them to make that mistake.  Having the lead means you are controlling the action, deciding how many chips must go in the pot.

Doyle Brunson wrote a famous book called Super/System, the book with the mysterious slash in the title.  Super/System has several sections, but most importantly it described Doyle's style of playing No Limit Texas Hold'em cash games.  Doyle is not a mathematical player, and in many ways S/S makes mistakes about what exactly is going on in the poker game, and some of the specifics are even completely wrong.  Regardless, S/S describes a very effective style for playing No Limit cash games, which is basically just to play very aggressive.  You do two things - play hole cards that can make big hands (Axs, pocket pairs, suited connectors) trying to make a monster that will knock someone out, and bet a lot.  Your hole cards will frequently miss making that big hand, so then you will be bluffing.  You also want to try to always be playing from late position and always taking the lead in the pot.  Don't come in early, and don't come in calling.  You come in late and raising, you take the lead, and you keep the lead by firing at the pot.  You don't make small stabs with a few chips, you make big bets, roughly pot-size, to put heavy pressure on them to fold.  They will fold too often, because most players do not adjust properly to very aggressive opponents, so your stack will grow from lots of small pots.  You will lose some big pots, because when they make a hand, they can slow-play you and get a lot of their chips.  That's fine, you're making it up in the balance.  For example, you might win roughly 90% of the pots, with 10 chips in each, and lose 10% of the pots, with an average of 50 chips in the ones you lose; your long term EV is 0.9 * 10 - 0.1 * 50 = 4 chips per hand!  The other thing is that since you are playing hole cards that can make big hands, you will frequently be on a "semi-bluff" instead of a pure bluff, so you will be showing up with hands that beat them.

Let's consider an example in more detail.  You see the flop from late position, coming in for a raise, with drawing-type hands.  You will wind up with a good draw (a flush or straight draw) or a good hand (set, two pair) about 15% of the time [@@].  You always bet the flop.  Your opponent will play a good top-pair (top-pair with ace or king kicker) or better hand against you, but let the rest go.  If he does have a good hand, he'll come back at you.  You then fold if you had junk, or you both go all-in if you have a good hand.  He has a hand to play about 25% of the time.  So, 75% of the time, he folds and you win the previous pot, say 10 chips.  Of the remaining 25% of the time, he comes back at you, and you let it go 85% of the time, so you lost your bet, also 10 chips.  The other 15% of that time, you both go all in, and you win 50 chips (probably because your stacks are like 200 chips and you win only part of the time you get all-in).  Your net EV is : -5 + 0.75 * 10 - 0.25 * 0.85 * 10 + 0.25 * 0.15 * 50 = 2.25 chips   So, this play is very profitable for you.  Obviously you both wouldn't play it exactly like this, in fact you can play it even better, but this illustrates the principles of how you're making money on these plays.  First of all, you are putting on pressure with pot-size bets.  This is big enough to make him fold most hands.  If he comes back at you with larger bets when he has real hands, you can get all-in with him, and *you* can choose when it happens so that you get all-in with your big hands or your good draws.