I think that all this kind of questions have to be answered with the same reply: "It depends on the situation". It´s true, every detail, every piece of information can change your decision. Every play depends on your position, your stack size, your opponents styles, etc.
But if you refer as a general rule preflop, again it depends on your style (aggressive or tight). For example, i´m tight and in a sng i like to play 9 handed at the beggining. So if i´m dealt KJ i won´t gonna play it. But other players are aggressive and they will raise with that.
Remember that all kind of styles are good if you play them correctly. Just define your style.
For starters..The Flop
Deciding whether to continue playing after seeing the flop will be your second biggest decision. It can also be one of the most costly decisions if you continue after the flop with an inferior hand. It is said that the flop defines your hand. That is because after the flop your hand will be 71 percent complete. Where does this figure come from? Assuming you play your hand out to the end, it will consist of seven cards. After the flop you have seen five cards or 5/7 of the final hand, which is equal to 71 percent. With this much of your hand completed you should have enough information to determine whether to continue. Poker Author Shane Smith coined the phrase “Fit or Fold. If the flop does not fit your hand by giving you top pair, or better or a straight or flush draw, then you should fold if there is a bet in front of you. If you played a small pair from late position and you do not flop a third one to make a set you should throw the pair away if there is a bet.
If you think you have the best hand after seeing the Turn card and are first to act, then go ahead and bet. Many players will try to get fancy and attempt to check raise in this position. If the other players also check, you have lost a bet or two. In low limit games the straight forward approach is usually the best as there are plenty of players who will call you. Make them pay. Why give them a free card if you don’t have to.
If another player raises on the turn and you hold only one pair you are more than likely beaten and should fold.
If you get to the Turn and you hold only two unsuited overcards (two cards higher that any cards on the board) with no flush or straight draws, then you should fold if there is a bet in front of you. Too much money is lost by players who hope to catch a miracle card on the river. The best hand you can make with two unsuited overcards is a pair which will probably lose anyways.
If you have been playing properly you will not see the river card unless you have a strong hand that is a favorite to win or you have a draw to a winning hand. Once the river card is turned over, you know exactly what you have. If you were drawing to a hand, you know whether you were successful or not. Obviously if you do not make your hand you will fold.
As with the Turn you should bet your hand if you are first to act. If you bet and the other player folds then they more than likely would have just checked if you had checked in an attempt to check raise.
When you get to the river there are two mistakes that you can make. One is to call a losing bet, which will cost you the price of a bet. The other is to fold your hand, which will cost you all the money in the pot.
Obviously folding your hand will be a far more costly mistake then merely calling a bet. If there is a slight chance you may have the winning hand you should call. I’m not advocating calling with nothing but you should call if there is a chance to win.
------------------------ Reading The Board
Your ability to read the board will help make you a winning player and it is not hard to learn. Since Texas Hold’em is played with community cards turned up for all to see, you can easily determine the best possible hand that can be made from the board cards and two unseen cards. It is extremely important that you learn determine how your hand stacks up against the other possible hands that your opponents may hold. Two situations should send up a red flag when you see them.
If there are three suited cards on the board someone can make a flush. If a player raises when the third suited card is turned over you should be wary of continuing. If there is a pair on the board a player can make four of a kind or a full house.
When you are not involved in a hand you should still pay attention to the game. You can gain valuable information about your opponents simply by observing what hands they play. It’s easy to determine the players who plays and suited cards, or single aces by watching the hands they turn over at the end. That brings me to one final tip.
NEVER SHOW YOUR HAND if you don’t have to. If you win the pot because everyone else folded you are under no obligation to show your cards. You don’t want to give away any information about yourself if you don’t have to And player who turn over their cards when they don’t have to are doing just that.
So yes most of the times I go by the "fit or fold idea". Yet on occasion I have been known to bluff.