Pairs
Preflop > Pairs > Draws > Big hands/Bluffing > Other
Pairs are probably one of the hardest hands to play correctly. Time and time again, people will put themselves in horrible situations with pairs and lose big against better hands. The key to playing them well is mainly to keep pots small and get information on your opponent.
Keeping pots small doesn't necessarily mean not betting. For example, let's say you have KQ in 8th position. The person in 5th position flat calls, and you also call. Everyone else folds to the big blind who checks. The flop is Q28 rainbow. Both players check to you. At this point you should bet because A: you probably have the best hand and B: you need information on your opponents.
Let's say you bet 2/3 the pot, the BB player folds and the other player calls. The turn is a 7, and the other player checks to you. Most people would bet here, but It's a much better idea to just check it. I'll tell you why- Since he called your bet, he must have something or at least believe he has something. Since there are no draws on the board, it's either a pair (probably a queen with a worse kicker like QJ) or he's slowplaying a big hand like trips. Now, if he has a queen with a worse kicker and you bet again, he might just fold it rightly assuming that you have KQ or AQ. However if you check it he'll most likely bet the river since you showed such weakness in checking, and even if he checks you can bet it and he almost has to call. If he does have a big hand, he'll assume you aren't very strong and he might even make his bet small to get you to call. Of course, you still have to pay him off a bit in this situation, but it's much better than losing all your money or having to fold when he potentially check-raises you on the turn if you had bet.
Of course, checking the turn isn't always the right thing to do. If you're out of position (you act first in a hand), you should bet it. This is because if you check it the other player can bet and you'll have no idea what he has. Betting here puts you at risk of being raised, but there's not much you can do about that. It's just one of the many reasons to avoid playing out of position. Another situation where you should bet is if there's a draw on the board like two cards to a straight (for example if the board is TJ34 and you have AJ) or if there were two suited cards on the flop (if the suited card came on the turn that's different, because there's no reason to believe he called your bet on the flop with two of that specific suit). The reason for betting here is obvious, you don't want to give draws free cards. In the case of a draw on the board I would recommend a full pot-sized bet.
