Condition yourself physically. Start a modest exercise program to help relieve stress. Drink more fluids and get plenty of rest to avoid fatigue, as we are more susceptible to our habits when we are tired.
Gradually reduce your cigarette consumption. Slow down from two packs a day to one pack, to half a pack, to five cigarettes; or, switch to a brand you find distasteful or change to a brand that's low in tar and nicotine a couple of weeks before your target quit date.
Find a new (and healthier) habit. Take daily walks, delve into a hobby or chew sugarless gum.
Talk to your doctor. He or she can provide some help as well, including recommending certain smoking cessation aides.