Most of the time the people who bluff and end up wining know exactly how to carry themselves, the game is about trying to deceive and confuse your opponents so that they may think wrongly about your motives.
A very important move to bluff and that is why it is said that experience counts in poker. If you are beginner and bluffing you would be skeptical but experience people will never show or you cannot find out easily if they are bluffing or not. It is also a art which is developed over the time when you play it.