The hardest part about quitting is breaking the habits that go along with it. For example, if you are used to smoking with your friends when you are hanging out together, it will be hard to hang around with them and not smoke. The best way to keep from smoking is to not put yourself in situations with people who smoke and to stay away from places where you are used to smoking.
Avoid places and situations where you normally smoke.
Spend a few days or a week away from your friends who smoke.
Go to non-smoking places with your friends, like the mall or the movies.
Don't drink alcohol. Alcohol will likely lower your willpower and increase your chances of having a cigarette.
If your family smokes, ask them to not smoke in your room.
Exercise. It will take your mind off smoking, make you feel better, and keep you healthy.
Plan activities during the first couple of weeks to take your mind off smoking. It will be easier to quit if you keep yourself busy.
Buy lots of carrots, celery, and other healthy foods so you can munch instead of smoke.

I was able to quit cold turkey five years ago. I failed several times before that but was finally successful. My wife quit at the same time but she used patches to help her along. They seemed to help. I think how easy it is to quit is how much will power you have. Some people are just programmed differently that it's easier for them to become addicted to substances like tobacco and alcohol. There are many treatments out there to help one quit and while you may not succeed with one, don't give up. Quitting is the best thing you could ever do for your life.