Ok, so im not a smoker, hopefully will never be one (im a 13 year old girl), but here are my ideas. They have never been tested so i dont know if they work - but they're the close to the other's ideas, and they're kind of like theropy help.
1) Write down your reasons on a piece of paper. Anytime you want a smoke, write down those reasons AGAIN on another sheet of paper. keep both. Look at those reasons. Write a list of what a cigarette will cost you. Write down those reasons. Take out a cigarette. Is it REALLY worth it?
2) Like Impervious said - Drink a glass of water, brush your teeth, take a jog - basicly, do a good habit every time you want to smoke. Replace a bad habit with a good one.
3) Take a cigarette throw it on the floor, then smush it with your shoe. Then pick it up and throw it in the garbage to keep the floor/Earth clean. DO NOT LOOK BACK.
4) Remember what your going for. If you can do this, you can do anything. Say, "I am _____ and I can DO THIS!!"