Choose a specific quit date. Instead of trying to quit each year on your birthday or for your New Year's Resolution, try quitting on a Monday! And not just next Monday - but every Monday. That gives you 52 chances in a year instead of just one chance––making it more likely that you’ll succeed. The Healthy Monday Campaign, a non-profit national public health campaign associated with the Columbia University's Mailman School of Public Health, encourages people to quit smoking and take other healthy actions on Mondays.
Between your decision to quit smoking and your "quit date", do not smoke the same brand. The difference in flavors and chemicals will make smoking less enjoyable, but not intolerable. Switching brands also helps to ‘de-automate’ smoking, which can help you become more conscious of your habit and increase your chances for success.
Remove all tobacco products, like lighters and matches from your home and office. Also, don't even keep a pack of cigarettes at your home, because it will make it easier to start smoking again.
That last step will not help people who have bummed a few thousand smokes in their life. In that case, refuse to open a pack. Keep it on you for at least a month, and maybe a year, until delaying yourself, distracting yourself, and denying that urge to open your pack is strong.