Wait until you are totally ready to stop, happy to stop and confident that you can stop before you have your last smoke.
Wait until the stress in your life is at a normal level. (i.e. not when you have just started a new job or you are moving house.)
Tell others that you have stopped and ask for their support.
Buy yourself something big, and pay for it out of your smoking savings - a constant reminder of the positive benefits of stopping smoking.
Take up a hobby - either something physical, so that you can see the benefit of not smoking, or something to do with your hands to occupy your mind.
Tell yourself you are a non-smoker and get on with your life.
Think about smoking often to remind yourself how awful it is and congratulate yourself on getting your life back.
Enjoy the rest of your life as a non-smoker.
Cut down - just stop, and only do it when you are ready.
Change your lifestyle. (if your social life suffers you will blame it on stopping smoking and resent stopping smoking. This will totally take the pleasure out of stopping.)
Make bets with your friends. (i.e. 'We'll both stop and the first one to smoke pays the other £100'.)
Compensate for smoking by eating more.
Keep a packet 'Just in case.'
Try to stop thinking about smoking.
Keep track of how long it has been since you stopped. (What's the point? - you are a non-smoker. Counting the days will only reinforce the idea that you have made a sacrifice.)
Smoke and make an excuse for it - 'It's Christmas', 'It's only a cigar - I don't inhale' These are the subtle smokes that set you back on the road to full addiction again.