I would recommend the tips in the No-Cry Sleep Solution book, as some of them were very helpful to me. They are also very gentle compared to many methods. Dr. William Sears also has some nighttime parenting books which touch on this issue.
Little babies are biologically geared to not sleep too deeply and to need to eat around the clock. Moms have higher prolactin levels and generally higher milk supplies during the middle of the night.
I personally refused to do anything that involved crying it out or not attending to my babies' needs. All of mine slept alone at some point, two much sooner than their brother did.
Good luck! This too shall pass