luigi,
a million dollar question!!
There are literally hundreds of "solutions" which you can buy (buy being the operative word)
I can only tell you about my own experience.
I gave up (20-30/day) in April 2001 after 25 years.
I used stubbornness and bloody mindedness, with no artificial substitutes.
I mentally set the date a week or so in advance ("when I finish this carton") and stuck to it. I consciously smoked my last one, and haven't touched one since.
Changed routines associated with smoking, eg after dinner have a cold drink instead of coffee. (My coffee consumption is now a fraction of what it was when I smoked.) Tell people and ask for support.
For the first couple of weeks I felt uncomfortable (not really ill) and the urges were strong and frequent. I just gritted my teeth. Gradually they become weaker and less frequent, and now I hardly think about smoking at all. It is no longer a problem. The main thing was the decision itself, then get throught the first few days which are definitely the worst. After that I found the greatest incentive was to think about how I would feel if I smoked a cigarette. Having tried previously I knew the answer. I would feel no better for it, I would hate myself for having given in, and I would have to start all over again. (And face the shame of failure).
Sorry to go on a bit, and sorry to be a bit smug. It isn't so easy, and really I was just stubborn.
Good luck, and I hope this helps even a bit. Do have a go, I'm certainly glad I did.
if you want further advice just post another question.