Rational Emotive Therapy (RET)
Learn more about Rational Emotive Therapy at CognitiveQuitting.com.
I put this one first because it can be - and IMHO, should be, - used in conjunction with any of the other methods listed in this section. It also seems to me to be closely related to the advice of Allen Carr, whose method is described below.
Don't shy away from what may sound like a technical discussion; RET basically is no more than a way of changing your attitude.