Here are some tips I found to help people while they quit smoking to not gain weight.
1. Plan activities for times when you have the urge to smoke a cigarette.
2. Keep your hands busy all the time (especially at night)
3. Carry a bottle of water with you whenever you can
4. Bring a healthy snack with you in Ziplock bags
5. Keep sugarfree gum, mints or even moutwash with you
6. Exercise!