The most important factor is that you have to want to quit, Anything less than 100% commitment is going to end in failure. Stop dead, all attempts at cutting back, gradually reducing the numbers of cigarettes is a waste of time.
Practical tips are
1 Drink plenty of water
2 Clean your teeth after every meal and snack, even if this means carrying toothbrush and paste around with you.
3 Don't eat sweets or chew gum. Anything that leaves a sweetish taste in you mouth sets off craving. You should aim at a sterile mouth.
4 No booze. That's the reason many fail. Alcohol sets off craving like nothing else. Strictly no alcohol.
5 Exercise and plenty of it. When I stopped after many, many failed attempts I suddenly had a compulsion to walk, run, do sit ups , any kind of physical activity seems to be of great help. I don't know why but in my case at least it really did help.
6 Be prepared for irritation, bad temper, moodiness and anger. It will last up to three weeks. You are a junkie and you are going to experience withdrawal misery.After three weeks all the physical symptoms will vanish but you will feel like smoking on and off for a year or two. Eventually the smell and sight of cigs will repel you.
Good luck. Remember you must be 110% commited and failure is not an option.