What helped me more than anything else was something that I thought was a dumb idea, but I tried it anyways because it was worth it to quit smoking. Someone recommended that you take a paper that has a table with several rows and columns, and carry it with you all day long. Every time you want a smoke, you can have one--but you first write down the time of day in one column, what you are doing in the next, what you are thinking about and feeling in the next one. Then go ahead and smoke. The trick was not to try to stop or cut down, just to take a few seconds and write that information out. Each time you smoke, you use a different row. By the third day, I had gone from a pack/pack and a half a day, down to 3 cigarettes.
That worked. I stayed quit for a few years after trying that one. Went back, then I quit again, and I've been cigarette free since the 90s.