Bluffing has nothing to do with your cards, it's the situation, your image, and your opponents that matter. If you're incredibly loose, then people will be more willing to call you; similarily, if your opponent calls almost every bet regardless of the board or his cards, he will most likely not be fooled by your bluff. However, if you manage to cultivate a tight image, people will be more inclined to lay down their cards to your bet. Also, you must take into account how much is in the pot, and how much your opponent has invested, as well as how many chips they have behind. If your opponent has bet a LOT and the pot is BIG, they will be less inclined to fold - plus, they most likely have a decent hand. However, you still may be able to bet them out if they have invested a small portion of their chips, and you can force them to put their whole stack on the line. This is even truer if it is deep in a big tournament. Conversely, if it is a small (or large pot), but the opponent has already put most of their stack into the pot, they will probably not fold - unless it is the bubble, which is why that particular time is a great time to take advatange of people. In conclusion, when bluffing, pay attention to circumstance and image, not cards.