I used to smoke between a pack and a pack and a half every day for 12 years. Five years ago I quit.
During the first ten years of smoking I didn't want to let go of it... I enjoyed it too much. My last 2 years of smoking were a constant battle of not smoking for 2 days and later retaking and making up for what I hadn't smoked by smoking double the norm. It got to a point where I was wheezing all the time, and climbing up 4 steps was something that left me panting for a half hour.
What I did was go cold turkey, but I programmed myself to do so. My birthday is in February, and in October of the previous year I decided I would quit smoking on my birthday... so basically what I did was smoke as usual and just try to enjoy it without a problem, but reminding myself that my smoking days were counted and that I'd quit in Feb.
The night before my birthday I smoked about 7 cigarettes in an hour, and those were my last. The disgust of smoking so many cigs in such a short time lasted for about 3 days, and after that I just focused on other things. I think it was the pre-programming what helped me overcome the instant cravings. After abut a month the cravings become more intense, but last shorter.. and after a couple of months the cravings are like when you feel like having some coffee and later forget about it.
The hardest point is about 4 months after, but at that time I was chewing nicotine gum... and what I'd do is (quite disgusting, I'll admit) keep the gum in your mouth all day (throw it out when you're going to eat and get a new one) and chew it about 5 times whenever you feel the cravings, and later just tuck it under your tongue or something... and take it out to chew again whenever you get the craving. My mother in law quit smoking at the same time as I did, and she used up about 2 boxes of nicotine gum... I only used about 10 pieces.
I would also smoke cigars about once a week with friends... which later turned to one cigar per month and eventually I even quit those. The cigars are good for a massive dose of nicotine, even if you don't inhale... but since your body is disposing of it, you might get a headache, and thus, not want to smoke
The hardest thing was giving up the pleasure of smoking at 5 moments: the morning smoke, with coffee... the poop smoke... the after sex smoke... the before bed smoke... and the after lunch smoke. And even now, five years after I quit, I still dream I smoke... and wake up feeling guilty.
All in all, I'm pretty glad I quit... and I doubt I'll smoke again. Although my wife smokes a lot and she does it right next to me. Don't be surprised if after you've quit, you start despising cigs... nowadays I can't have someone smoke too close to me because the smell makes me nauseous.