Stealing the pot now and then can add a small gain to your bankroll. Many small gains lead to big gains over time, thus making a steal a very valuable play. However, stealing the pot is a very dangerous and risky method of play. It works only under certain circumstances, so you need to either have perfect timing or be willing to face great risks. Stealing the pot consistently will also lead to an awareness amongst other poker players of what you are doing, thus causing them to react aggressively. This is an indication that you should not try this strategy regularly.
So when is it appropriate to steal a pot? For one, the pot cannot be large. Large pots offer good pot odds to other players so even if they have only a few outs, it will be correct for them to call your bet. A small pot, then, is the only time you should attempt a steal. You also want to make sure that you at least have something in your hand. Making a large steal bet with 2-7 off suit can be a disaster unless you are attempting a stone cold bluff. With a steal, however, it is much more to your advantage that you have at least ace high in your hand so that you can gain some credibility if you are called. Remember, a steal is not the same as a bluff. They serve the same outcome, but by two different methods. In order to make a steal reputable you need to have more than junk cards. This will allow you to replicate the steal at a later time. If they have seen that you would only make such a play with an ace high or low pair, they will be more likely to fold. An exposed bluff, on the other hand, will only encourage people to call your bets more often and the pokerparty will turn dark quick.