1) Not raising enough first to act pre-flop. How many times have you seen someone minimum raise with aces and the big blind call them and bust them when they hit some miracle flop? I know I've seen more than my share. Why is this such a problem? First, the big blind is receiving the correct price to make the call with nearly any two (and if you are in the big blind and someone min. raises, you are almost ALWAYS correct in calling).
Let's say the blinds are 200/400 and the player with aces makes it 800 to go. Everyone folds to you. You now have to call 400 to win 1400 or 3.5:1 on your money. If anyone else has called the raise that number jumps up even higher. The problem with wanting to induce action by making a minimum raise is that you get the exact action you don't want... a random hand that you cannot discern.
If you make a regular raise, you can at least narrow the probable range of hands your opponent has. A correct raise should be 3 to 4 times the big blind. This will generate the action from the hands you want action from, and garner you the respect you want on the hands you are stealing with. Be consistent with it as well - it disguises the strength of your starting hand.
2) Not re-raising enough. Here's the scenario. The blinds are 100/200 and you raise - first to act from the cutoff - to 600 with 6-5 of spades. Joe Schmo has A-K in the BB and reraises 600 to 1200. You now have to call 600 to win 1900 or over 3:1 on your money, and even though you know you're behind, you're justified in calling here because 1) you have position and 2) you are only bigger then a 3:1 dog on over pairs and 3) your hand plays very easily post-flop.
If you are going to reraise a raiser, you generally should make the raise big enough to 1) punish them if they do choose to call - that is, give them an incorrect price and 2) get the hands that you might want folding (like say 8-8 when you have A-K) an opportunity to fold. Don't give your opponent a reason to call here. Furthermore, by being consistent with your reraises, you'll find that when you do this enough, you'll eventually get played back at. The beauty of this, of course, is when you actually have the monster. A good raise is to make your raise 2 times the size of your opponent's total bet. So in the above example, you would raise 1200 (600*2) to 1800. Your opponent would have to call 1200 then to win 2500 or just over 2:1.
3) Over committing. One of the biggest mistakes poker players make is over committing themselves when they can obtain the same information for a lot less. Example - you raise pre-flop with A-K and get one caller. There is 10,000 in the pot. You have 20,000 in chips left. The flop comes queen high. You bet the pot and your opponent moves all in. You've now put yourself in a very tough spot. The pot is huge and you only have 10K left, but you have at best two over cards and nothing more. If you had made a smaller, more standardized bet of 1/2-2/3 pot, you could have escaped from the hand and still had room to play. By betting so much on the flop however, you have essentially committed yourself to the hand despite likely being a favorite. You can find out the same thing you want to know by betting half pot as you can by betting pot.
4) Not betting enough. The opposite problem to #3. Nothing is more fun in poker than when someone makes a minimum bet on the flop when you have missed, but have outs to the winner. Say for example, you called a raise with A-Q and the flop comes J-10-4. Your opponent makes a minimum bet of 1000 into a 10,000 pot. Even though you have nothing, you should call here, because you have outs to the win and the price is correct. By betting small, you generally do three things: 1) Let hands not as good as yours catch up and pass you. 2) Not get any information by your opponent's call. Does she have a made hand or is she drawing? You really can't tell because she could be calling with anything. 3) Set up a later bluff/steal from your opponent. If you bet weak on the flop and turn, your opponent might very well put you to the test on the turn. And while that might be an advantage to making this small bet (to induce the raise), you have to be fairly certain your opponent is going to do that. There will be times where you just want to win the pot - the minimum bet is not going to accomplish that. If anything, it is going to tell your opponent you are weak and he is going to test you.
Be smart with your bets. Think about what you are looking to accomplish and make a bet that will do this.
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