Joey, another important thing is to always know exactly why you make each bet, and have a pretty good idea of what you will do if called or especially raised. A lot of beginners find themselves making bets where they aren't really sure if they're bluffing or protecting a weak made hand or what. There are two parts to this:
1) Your bluffs should come in two varieties. Semi-bluffs, where you go all-in with a decent draw. You're hoping they just fold, but you still have a chance to win if not. The rest should be stone cold, where you have absolutely nothing, and leave yourself room to fold if raised. What you don't want to do is be bluffing with weak draws or pairs and find yourself in a position where you have to give up your stake in a big pot with a hand that has some value. Poker's a complicated game, and I cannot overstate the value of keeping your decisions simple.
2) Recognize when a hand, even a very good one, only has value as a bluff-catcher. A classic example is when you've flopped a big hand like a set or a straight and a potential flush draw comes in. This makes the board scary, and if the pot is small, most opponents aren't going to be calling many big bets unless they have you beat. Another example would be if there are 2 pair on board, and you have one of the smaller one in the hole. If you're opponent bets into you, raising your full house has no value; almost everyone will be folding any hands that you can beat (and thus the bet brings you no benefit) and calling/raising when you're losing.
When making any bet, ask yourself, what am I hoping to accomplish? Do I want to fold everyone out, to gain information about my opponent's strength, or to get action and build a pot? If it's the last one, what kind of hands could they feasibly have that would call, and what kind of threat does that pose?
