Betting, raising and check-raising are instrumental weapons in a poker player's arsenal. You should generally bet or raise whenever you feel you have the best hand. This is done to increase the amount of bets in the pot and also to charge drawing hands the maximum to make their hand against you.
If you are the first player to enter the pot then raise with any of the hands in the hand selection groups according to your position. For instance, if you are one spot off the button and no one has entered the pot, then by all means raise with your pair of 6s - chances are good you have the best hand.
If there have been callers in front of you, then raise with all the hands from the early position group and call with all other hand groupings according to position. If there has been a raise in front of you, then re-raise with all of the early position hands or call with any of the middle position hands. It is difficult to play any of the late position hands in this scenario because they are vulnerable. The exception to this would be calling with higher suited connectors or small pairs if there have been at least three or four other callers in front of you. This will ensure that you are receiving the proper pot odds to make a call. Note that you are hoping to flop two pair, a set, or a straight or flush draw in these cases and will fold on the flop if you miss.
Additionally, you may play a very strong hand, such as a pair of aces, deceptively pre-flop. The intention would be to check-raise your opponents when someone raises behind you. This play depends on being relatively certain that someone will raise behind you and should be made when your opponents are overly aggressive with weak holdings, or relatively tight and quick to fold to raises from early position.
The flop will give you a much better idea of your hand's value in relation to the probable value of opponents' hands. For instance, if you raised from early position with a pair of 10s and had four callers, you must legitimately fear overcards. If the flop should then come with two overcards like an ace and a king, then the chances of you having the best hand are much slimmer than they were pre-flop. If, however, the flop comes with all undercards that are not of the same suit or connected, then there is a very good chance your 10s are best and you should lead out with a bet.
If you should flop top pair, two pair or a set, you should bet or raise on the flop aggressively if there is the possibility of a straight or flush draw on the board. Although it is tempting to slow play strong hands, it is also important to protect your hand when you are ahead by not allowing players to check behind you and see another card for free.
If you flop a straight or a flush draw you will typically want to see the next cards as cheaply as possible. If you are in late position, however, you might consider betting or raising on the flop with a draw. Often your opponents will check to you on the turn as they fear a raise from you in late position. Depending on the strength of your hand, you may choose to bet again and perhaps force opponents to fold. If you feel your opponents are too strong to fold, then you can simply check behind them and see the river card for free. This can be a very effective use of a bet or raise from late position.
Check-raising on the flop can be an effective tool in making a call too expensive for other players to see the turn card. This is an effective tactic to use if you have flopped a hand that is vulnerable to overcards or draws. Check-raising works best if a pre-flop raise comes from a late position player and you feel that the action will get checked around to the raiser. If they should then bet out again on the flop, you can at that point check-raise the raiser, making it very difficult for the players behind you to call two bets cold.
The Turn and the River
On the turn and the river you should continue to bet made hands such as top pair, two pair and a set. Additionally, you may have completed a draw at this point and as such should be betting, raising and possibly re-raising depending on the strength of your made draw. It is important to remember that if another player plays back at you aggressively then it may be time to slow down. If they're not afraid of your bets, show caution. For instance, if you are betting top pair and are raised by another player on a board that shows a possible straight or flush after the turn or river card, you should seriously consider only calling. This player's actions indicate the hand he or she was looking for has been made.
If you intend to check-raise with a very strong hand, consider check-raising on the turn instead of the flop in instances where your hand is strong enough to withstand your opponents seeing the turn card for cheap or free. This is particularly valuable if another player has taken the lead in betting and there are other callers, as you will now be able to get additional bets into the pot. Beware of waiting to check-raise on the turn if the turn card could make a better hand for an opponent such as a straight or a flush against your set or two pair for instance.
Betting, raising and check-raising can also be powerful weapons when trying to deceive or bluff a player out of a pot. A well-placed bet or check-raise can also sow the seeds of doubt in your opponents' minds and cause them to lay down a better hand. It is important, however, to use this tactic sparingly and in the appropriate situations. The danger of making this play too often is that your opponents will stop giving you credit for having good hands and start calling you down as they correctly suspect you are bluffing.