I have been completely clean and weight-lifting for six years, and had a five year period prior to that where my attitude was, "If you have it, bet your ass I will try it" K, E, coke, crack, Horse, RXs and so on.
One night, I was particularly high after consuming ~1g of what I thought was pure MDMA, but later turned out to be a mix of lysergic acid [acid], PCP and MDMA. I believe the concentration was later revealed to be primarily MDMA, with lysergic acid and about .1% PCP cut into. Anyway, I digress: after a very odd and eventful night, a Meth dealer named Mark, who did not particularly like me, and who lived in horribly dilapidated apartments ~three miles from my house, made me walk home at 5:30 A.M in the middle of January. This doesn't sound that arduous from the outset, but let me lay a few things out:
a) This was in Southeastern Alberta, where the average low without wind-chill in the month of January is -16.0 C [3 F]. The only reason the average is so high is because Chinooks comprised of warm coastal uplift air from the Rockies descend incredibly quickly and can produce + temperatures in a few hours. I would say a more fair estimate for "cold days" in January is -30 C [-22 F] w/ the windchill.
b) I was high as balls. This is the most important condition, because three miles in -30 C weather may as well be the Boston Marathon carrying Rosie O'Donnell. I was having severe auditory and visual hallucinations, and to this day I am incredibly surprised I made it home.
Literally the first thing I did upon waking was call my friend and say, "I'm done". The harshness of the experience itself wasn't necessarily the motivating factor for the decision, but rather, the revelation of, "A smelly Meth dealer named Mark just kicked me out of his dilapidated apartment at 5:30 AM; what the **** am I doing with my life?" So, immediately that day I gave my friend my last few g of marijuana, my last smoke pack and have not done anything since. No nicotine patches or self-help groups, just a pair of testicles and a real desire to quit.
In my completely honest assessment, the physical-mnemonic devices and preoccupation techniques you frequently hear about are utterly useless with a real and lasting desire to no longer share a relationship with tobacco. I also don't mean to devalue Suncloud's, Easy's and the others' suggestions, but merely to suggest they are functions to facilitate the realizing of your desire to quit, as opposed to techniques to produce the desire to quit itself. Unfortunately, the production of that desire is often most arbitrary and highly personal, stemming from a motivation only known to you!
A helpful to tip to search for that desire, though, may be to conceptualize 'smoking' not as a habit, but as a deep-seeded destructive relationship: the bonds of a relationship are much more ossified [rigid] than the symptoms of a habit, and therefore breaking each one takes progressively more personal techniques. Quitting tobacco use is like trying to break up with a girl who wrecks all your **** but is the best sex you have ever had: you say you want to b/c she is a freak, but the sex feels so good it is hard to sever that relationship until you realize how it is affecting your life!