Smoked for nearly 20 years - quit 8 years ago; best thing I ever did.
I'd tried plenty of times, stopped for over a year at one time, but started again.
The way I stopped for good, was I was due to go to China on a business trip with a very busy schedule. I decided weeks before that I wouldn't take any ciggies with me, and I started to picture myself in situations where I'd usually smoke; in the car; in a bar; after a meal etc and also turning down offered cigs - in my visualisations I'd say "no thanks, I don't smoke".
In China I was so busy and it was so interesting, that it took my mind off them to some extent, and because I'd been visualising being a non-smoker, when I got back after the trip, it was easier for me to carry on.
First thing though - you've got to want to stop permanently or it won't last. You'[ve got to want to stop being a cigarette victim, always needing to know you've got some or where you can get the next pack. After you stop you'll realise how much ciggies controled you - if you want to stop you have to be the boss, not them.
My circumstances where a little odd and hard to replicate - if I had to stop again I think I'd go down the hypnosis route. Basically it will rewire your subconscious to make you believe you're a non-smoker the same as my visualisations did.
Good luck!