Chances are
that if you have to think about whether or not you should try to bluff your opponent, he already
knows your bluffing. Playing poker is all about decision making and reading your opponents.
You have to be able to think smart when a lot of money is on the line. Knowing just the right time to bluff can be the difference in hundreds of dollars. If a player has a short stack and already has some chips in the pot, it might not be a smart move to try to bluff because he will just push all in.
If you have been pegged as the player that only plays when he has good cards, now is the perfect time to start bluffing. Since your opponents think you have something, they are less likely to call. This is a good way to take down some pots at their expense. Just don't get too cocky.
If you can put your opponent on a weak hand then you should be able to bluff him out with a big enough raise.
Don't be afraid to pull out the check raise either. If you feel someone is trying to buy the pot over and over again with a weak hand, just check, and when they make their small bet to buy the pot, come back and re-raise him.
This is a move that can quickly get any wannabe's out of a serious pot.