This is the word everyone associates with poker and the word that everyone knows, even if he has never played a hand of poker in his life.
Do not expect to start bluffing the first time you play poker.
In order to be a good bluffer, you need to be a good player. You also need to use your instincts and courage. You can't just decide to bluff at any time during any hand. You need to pick the right situations and the right opponents. When you're getting started, try not to bluff. Even professional players rarely bluff. Experience, knowledge of the game and of your opponents will help you to pick the right times to bluff.
There is no magical formula on how to bluff. Someone who's trying to sell you one is probably bluffing.