I think that cnj gave you a good idea, but I also recommend speaking to your doctor. He can help tailor a plan specifically to your needs and habits. OR you could call a quit smoking helpline, they should have knowledge and resources for pregnant women as well.
Best of luck...I think it's a wonderful thing that you want to cut down on your smoking and quit! Baby's lungs will surely thank you..and yours, too! ;-)
What I did was just cut down until I quit. I was a pack every 3-4 days which isn't as bad as some with the pack a day but still bad, but I limited myself to 4 a day until it got down to 2 and now I've quit. So far 2 days good. Also pregnant with #2.