I was a smoker, i smoked throughout my whole pregnancy with DS1. I had a perfectly healthy baby BUT now i am regretting it as he is not a huge eater and sometimes i think maybe its coz i smoked. I gave up 2-3 months after having him, and i did it like this:
1. If you smoke 30 a day cut back to 20 within a week. That way you are still getting the "hit" and the hand to mouth action. I used to eat a carrot stick when i wanted a smoke.
2. If you smoke inside get outside and have it!! That way you are going somewhere different so then your not as comfy while doing it. (that was hard for me)
3. By week 2 cut down to 10-15 a day. (i only smoked 20 to start off with so it was a little easier for me)
4. You will soon start to not need a smoke and just automatically have less in a day.
5. over the next few weeks cut your intake down a smoke or two a day. I used to get the amount of smokes i wanted to aim for that day (say 3) and get them out and put them in a seperate packet. I would space them out. I would light up a smoke and have a few drags and put it out for next time.

Please note, this may or may not work for you. It did work for me, although this is a guide to help you with the outcome YOU want. I would adjust it to the way you want to do things.
Goodluck with your decision on quitting, i can honestly say that is the best decision i have made for my health and you will be surprised at how strong willed you are to do it.