Try to stay away from people, Because admit it or not, you are going to be a complete asshole for 3 days. Sleep as much as possible. And replace the smoking with something (if push-ups work for you, more power to ya) My replacement was apple jolly ranchers. I probably ate 15 pounds of those things in the process of quitting.
Another thing that helped me was to have cigarettes on hand. Its one thing to quit because you want to, its another thing to quit, and not have any on hand. That puts you into a semi-panic state. You are stronger than the cigarette. It does not control you. I held on to that pack for years.
*edit* Thread from the dead. I'll leave the info for the next run.