Personally I disagree with BlingBling. I think you need to crucify yourself if you lapse, even for a drag. I found that taking a completely negative view of smoking helped. Just walking down the high street I hold my breath now when somebody is smoking around me. I have built myself up to absolutely detest the smell. I attempted to give up many times and often faltered then worked my way back up to 20 a day. The last time I gave up, I did exactly that. I stopped dead in my tracks and went from 20 a day to nothing. I've not so much as touched a cigarette in about 18 months now and I feel immensely better for it. I feel guilty if I DREAM about having had a cheeky cigarette, which does happen from time to time (the dreams, that is).
Best of luck, the first week 48 hours are the worst (chemical addiction). It quickly gets easier from then in (habbit).