Another little tip I found particularly useful when I first started out was not to look at my cards until it was my turn to act. Two reasons here:
1. Sometimes you look at your cards and get an idea what you want to do. Action then takes place before you, and you still carry through with your original idea, even though the previous players action may scream "fold" at you. Similar to Gers tip of not getting married to a (weak) hand.
2. It gives you the opportunity to watch players as they act. You"d be surprised what you can pick up.
Story time, just as an illustration. This may have been at an APAT event, then again, it may not have been. A player was directly on my right (unfortunately) and was looking at his cards as soon as he got them. If he liked them he placed them on one side of his chips, and if he didn"t then he placed them on the other side, making it easier to slide to the dealer. He was doing this even when he was in the blinds.
As well as watching other players, be aware of what you are doing. My method is to (try to) do the same thing every hand, bet exactly the same way, raise the same way, pick the same spot at the table to stare at each hand you play etc.
Whatever happens though, have fun. If you can get yourself to an APAT National or Regional you should be guaranteed a pleasant experience.