One thing that's always helped me is let your smoking buddies know what's going on. They don't need to know your reasons, but at least tell them not to pass you the bowl on breaks. If you can go for a week or two of not smoking you're almost there. One way I successfully quit was to buy some super crap weed. Sounds funny, but when you get a really strong craving, light that up and it should make you never want to smoke again! I've heard nicotine patches and gum can help although I've never tried that myself. Main thing is you need to be aware of your triggers and habits so you can beat it.

Try these:

Quitting Smoking / Smoking Cessation Center: Find in-depth information to help you stop smoking
A Within-Subject Comparison of Withdrawal Symptoms During Abstinence From Cannabis, Tobacco, and Both Substances