How do i get my son to sleep in his crib all night?

I have a 3 month old and we are starting to put him in his crib because he was getting to big for the binet. He is a very crazy sleeper...constantly moving it seems like. In order for him to go to sleep in his crib we have to make sure we rock him and soothe him until he's out cold. We then can lay him in there and he will sleep for about 4 hours. He will wake up screaming and we go and put his pacifier in his mouth and he will be fine, but only for about 15-20 minutes. Then we'll have to do it over again, and this is how the rest of the night goes. Some nights I'll admit that I get really tired of going in there and giving it to him so I bring him into bed with us and as soon as I do that he is back to sleep. And he will sleep fine all the way until about 8:30 the next morning. I don't want to keep having him sleep in our bed because I know in about 8 months I'll b e regretting it! How do i get him to sleep through the night?