It has been about 2 or so weeks for me. The way I did it was stop buying packs a couple of years ago. My girlfriend smoked, so I started only really smoking around her, and the odd friend that was willing to lend a smoke. After a while you only think of smokes when you see others smoking.
I know the feeling of wanting, and not having sux. I smoke weed, so that helped me a bit I guess (cause I still smoke something).
After a bit your want for quitting overrides the cravings..
Just try really hard to be in controle of your body, and not the other way around.
GOOD LUCK. Have fun with the mood swings!