I quit three years ago almost to the date.   Two packs a day down to nothing.
-  stock up on food
-  buy popcorn, peanuts, or what you like (see below)
-  empty all ash trays
-  take out the trash
-  lock yourself in at home

Now, when you feel like a smoke, one piece of popcorn (or what ever you have chosen to busy the mouth.)  It's slow going but food, even popcorn, calms the urge. 

Lastly, when you do emerge from your house - don't go out without gum in your mouth!