There are two times to bite a lemon:
1) At the time a craving FIRST begins. There is no better crave buster than biting into a whole lemon, peel and all. The taste of that fresh sour lemon juice running over your tongue and into your mouth is a sensation that will immediately remove all thoughts of smoking from your mind.
2) When you have allowed a craving to build to the point when you may be considering giving in. See explanation in #1 above.
Follow the link to see MY own personal lemon after the first time I bit it. ;-)