It is also said that it helps to make your last experience a bad one, if possible. I myself got sick a couple of times from the combination of alcohol and nicotine.
I think that giving oneself a good fright also helps. This activates the emotional/subconscious part of the brain. Ways of doing this include looking at articles which describe the last stages of lung/throat/tongue cancer. Photos too, of people with tubes coming out of them.
The actor Yul Brynner died of smoking-related cancer and said he wished he'd never touched the bloody things (or words to that effect).