In-depth theoretical poker strategy is favoured by poker authors and fanatics. The first need something to write about, and the second need something to talk about. There is a separate school of thought that plays a much simpler game. Their game is no less effective, simply simpler. The Greek Maze is the straight hallway with several branches off of it, but the way out is at the end of the hallway. Try to make things complicated by travelling down the branches, and you'll just get more lost. Simplify by walking straight down the hallway, and you find your way out. What the hell am I talking about? The need to sometimes simplify. Poker is no different that anything else; it can studied to death. And the learned player definitely has an edge over the one winging it. But, a player can excel in poker by relying on gut and simple thought process, instead of mathematics and poker theory. For your use below is a simple chart outlining your options in a betting round.
Aside from the draw, all decision-making in poker is made on the betting round. A lot of thought can go into those decisions, but the decisions themselves are simple ones. Each of the point forms in the image below is a link to further explanation found beneath the image. Note that this deals with simple poker-playing. While it does take bluffs and slowplays into consideration, it does not take any of the advertising into consideration that you may use to deceive other players.
Nobody has bet before you and your hand is weak enough that you are hoping that you can stay in this game for free. You believe there is a chance that everybody else will also check, allowing you some free cards at no price. If somebody does bet, you will need to re-evaluate your hand, because the option to stay in for free is gone.
You are holding a strong hand. Your goal here is to check, wait for somebody else to open the betting round, see that bet, and then make an additional one of your own. You are initially suggesting a hand of no strength looking to stay in for free. The player who makes the bet only does so, not thinking there was another strong hand at the table. You also acquire information this way. Since there was no bet to you, nobody has suggested anything of their hands yet. In also declining to start the action, you put the onus on somebody else to make a move. This however is where check-raising can backfire. If nobody bets after you, then you have just lost out on a round of bets and have allowed everybody to stay in the game for free, possibly getting the free cards that they need to beat your hand.
You are holding a monster. You have so much control over this hand, that your goal has gone from trying to win to trying to maximize the amount of money in the pot that you're about to win. To bet outright might cause some folds, but to check keeps everybody in and forces another player to start the action (hence, you acquire information in the same way as check-raising). You also have no worries about letting players stay in for free because you're certain they won't get the cards they need to beat your hand. You need only ensure that you are actually getting more money in the pot in the long run. To slowplay to the showdown would mean there's no money in the pot. You will have to make your move in a later round.
Strong Hand (Bet)
You are certain that you will be able to make a bet here and not lose so many players that there will be no pot to fight for. If the table is loose enough, you can make your bet and keep enough players in. Or, you are playing a lower strong hand, in which case you want to get rid of a few competitors. Your bet will eliminate some players from the pot, increasing your chance of winning.
You cannot win the pot with the hand you've been dealt unless you convince EVERY other player at the table that you have a strong hand. A bet suggests strength, which is what is missing from your hand. Note that a bluff that doesn't fold every player by showdown is a failed bluff, and a waste of money in the end.
Your hand is neither strong nor weak. You may win and you may not win. The only way to be sure is to stay in the pot, but only if there is enough money in the pot to justify staying in. The pot needs to be sizable enough to justify you adding more money for the chance to win it.
You are holding a very strong hand, but rather than add to another player's action, you suggest that yours is not a hand worth re-raising on. Players to your left would otherwise be forced to call a double-bet to stay in. This way, you encourage them to stay in by only having them see a single bet. Arguably, if the original raiser was sitting at your left, then everybody has already seen his bet except you. In this case, you might be more inclined to bet since players are more likely to see two bets individually than a double-bet at once.
More of a call-raise, you see the original bet and call in the hopes that a third player will re-raise. When he does, you also see that bet, and then raise a third time. This causes players to see three individual bets. When the smoke clears, there will be far less players in the pot. Like any check-raise, note that if nobody raises after you, your plan has failed and you just lost out on a bet that you were willing to make.
Strong Hand (Raise)
If a raise makes players double-check their hands, a re-raise makes them even more uncertain. The re-raise sends a message to the original bettor that there is another competitor, possibly causing a fold. It also sends a message to the other players at the table that their hands had better be good to stay in; it's unlikely you and the other bettor were both bluffing.
Like the strong hand described above, the re-raise makes people think a lot harder about staying in. But, the re-raise bluff is a brave move. You are hoping that: i) the original bettor was bluffing and will fold from your bet, or ii) the original bettor was not bluffing but is concerned enough that you have a better hand that he folds. Also take note of those players that see both bets and call. They're the ones with legitimately strong hands. If you can't bluff them out on later rounds, get out of this hand...the jig is up.
Put a fork in you...you're done. Folding is the last outpost of the doomed. There is no greater finality in poker than the fold. It signals that you are out of the running.
If there is a worthwhile chance to win, then folding is obviously your last choice. But, where calling means aimlessly throwing money away, you do well to exercise the better part of valour.