Stosh:
I stopped smoking for 3 1/2 years.
I set a general date (but not a specific "deadline" for stopping. Prior to that time, I re-affirmed daily that I was ready to stop, and the reasons why. In the meantime, I switched brands from Marlboro Reds to Camel Lights for a couple of months; And then to Camel or Merit Ultralights. At the same time, I observed a strict "packs per day" limit to ensure I wasn't compensating for the lowered nicotine levels.
I made it a point to remind myself daily of tangible benefits that I knew would be a result of the decision: No more carpet or table burns, or pinhole burns on clothing and auto upholstry; No more odors in home, auto, or clothing. No more expeditions at 3 AM for an open store. Better stamina under heavy exertion. More pocket money.
As bizarre as it may seem, I sniffed an ash tray each morning to remind myself what "cigarette odor" must be like for others.
I determined that I was spending around $150 per month on smoking - So I resolved to save $75 each month in an account towards anything I wished to use it for; And apply the difference towards bills (I was badly in debt at the time). This ensured that I "received" regular, tangible rewards for not smoking . . .
I avoided situations and environments where smoking was a large part of my routine. "Coffee and a cigarette" became "coffee and a pastry", and I gradually cut way down on the coffee, too. I had stopped drinking prior to my decision to stop smoking, which was a helpful bonus - If I were loaded, I would "forget" that I wasn't supposed to smoke. Watch out for that trap.
I made a decision to stop indulging in scenerios where I just sat and smoked - like extensive TV and movie watching. Gloaras made a great point - Sex is a wonderful alternative to "too much time on your hands", and it just gets better as your stamina improves.
Carrot sticks, mints, gum, and toothpicks became the "preferred" oral substitutes.
Isla provided an important point - you don't just make a habit "go away" with sheer willpower; You need to find a positive substitute. Some people choose to start a light workout or running program.
The first 3 to 4 weeks are the most difficult time. In the worst-case "urges", I simply postponed that next cigarette - Five minutes, ten minutes, an hour - whatever. And then postponed it again, once I made that goal.
One other thing - Although I told people close to me that I intended to stop smoking as a warning of sorts for the "anxious" period that lasts a few weeks, once I did stop, I simply said, if anyone asked: "I don't smoke".
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Post script:
From the tone of my initial statement, you may infer that I resumed smoking, and you would be correct.
I went through a particularly stressful period in my life. Without all the sordid details, you will simply have to accept my assertion that to resume smoking again at that time was the least destructive (short-term) outlet available to me. I made a concious and considered decision to start again.
In hindsight, and although I regret the time lost, I wouldn't have made a different decision.
I am currently back in the "nicotine reduction phase", and anticipate that I will stop completely by the end of this year.