1 Betting out of turn :

You must wait until the player to your right acts. If you bet out of turn this could give an unfair advantage to a player that did not act yet. If you raise out of turn a player that might had called could fold. Or if you fold out of turn you are giving an advantage to the player on your left who now knows you won't raise.

2 Not knowing what the bet is :

You have to know what the bet is when it is your turn. After the turn in a limit game the bets are double the amount they were before and after the flop. You must also be aware if the bet was raised.

3 Folding instead of checking :

Sometimes if the player does not like the flop or turn he will immediately fold when it is his turn. If you are first to act you can check. If everyone else checks, you get to see the next card for free. The same is true if everyone checks before it is your turn, you should also check. The free card may just make your hand.

4 Throwing chips into the pot :

Place your bet in front of you. This way the dealer sees that your bet is correct. He will scoop them into the pot.

5 Not protecting your cards :

Place your hands or a chip on top of your cards. If another player's cards mix with yours when they throw in their cards your hand will be declared dead.

6 Throwing a winning hand into the muck. (Discards) :

The cards speak for themselves. Don't immediately throw in your cards if someone calls out a better hand. The dealer will declare the winner of the hand. If you missed a better hand than you thought you had you might just be the winner.

7 Not controlling your emotions :

Keep your emotions in check. The table is not the place for foul language or temper tantrums. It will not be tolerated. Besides it makes you look foolish. Veteran players as well as new comers occasionally make this mistake.