Where do you work? Are you allowed to smoke there? If so, stay out of the smoking areas. If not, don't go outside with the rest of 'em. If you work in a restaurant or a bar where people can smoke, well, I've been there, and I wasn't able to do it then.
Go out less. Especially for the first three or four weeks. Untill those base cravings go away, you will not be able to control yourself when out. If you can't not go out for a month, you are not ready to quit. I've been there, and I wasn't able to quit.
When you get through the first month, watch for the next waves of addiction. I went through hell 4 months later, seemingly for no reason. About 14 months after quitting, I went through some personal stuff, and bought a pack while drunk. I was hooked again after that. Be watchful even after you feel you've "quit."
Good luck.
And remember, it only hurts for awhile.
Edit: My withdrawl symptoms included a lot of irritibility, fatigue (slept for 16 hours a day), constant stupidity (lack of ability to concentrate, even to pronounce simple words in conversation) a lot of nervous eating and drinking pop (I gained 10 pounds, don't use Cram Soda as a replacement), and periodic cravings that almost hurt. Those come in waves though.
In short, you will go through hell for 3 weeks. But it goes away, and afterwards it doesn't seem too bad.
Good luck.