Here is what I shared a few months ago with another mom with a similar situation....I hope it helps or gives you some ideas!....
Well, I'll share what I have done and you can take it or leave it....I have 6 kids and they have all pretty much slept through the night at 4 months with this method:
I allow my infants to stay up as long as I do so that when I sleep, they sleep too! When they get older and older, I gradually put them to bed a half hour earlier...then another half hour earlier.
Usually I put them on a 4 hour feeding schedule....6pm until 10 pm is rough, they are tired and I'm tired, but I stretch it out so that they are good and hungry and good and sleepy so that they can survive the night. After the 10pm feeding, I put the baby in her crib with a pacifier. During the night if she cries, I get up put the pacifier in her mouth, but DO NOT pick the baby up....baby learns that it is not time for all that, it's time for sleep which means staying in bed. I will rub her back for a few minutes to calm the baby down, but make sure the pacifier is in and the baby is comfortable. I leave and go back to bed. If she cries again, I will let her cry for about 5 minutes and then get up and repeat with pacifier and calming her down. Each time she gets up crying, let her cry longer...10 minutes, 20 minutes, etc.
I know, this is an agonizing process, but it should take a few nights for her to learn the process and for her to realize that it is time for sleep and quiet. If you have ever watch Super Nanny, she uses a similiar technique even with older children. You are the one who has to be consistant...if you relent, it WILL NOT WORK!!!You have to stand your ground on this and if you do it seriously should only take a few nights for the behavior to be learned and followed by your baby.
I think it is great that you are starting early...I have friends whose 10 yr. olds STILL don't sleep through the night because the parents never established routines and rules for bedtime, falling asleep on their own, and staying in their own bed!!! I would have died if I didn't start early with mine....can you imagine 6 kids in bed with me and my husband at various times of the night!!! No thanks!
Anyway, good luck! It is not easy, but soooooooo worth it!! Be Tough!