Having a great setting, beautiful light, and a gorgeous couple are all great things for taking good pictures. But that's just part of it, the moment between a couple has to be exciting as well. We are all about the moment, and you can't exactly "pose" a moment. I try and get my couples comfortable by having them interact with each other as much as possible. I might also give them some direction and have them snuggle up, but then completely separate them and have them come into that pose. It looks too stiff and well-posed if you just take the photo after you set it up. Sometimes having a short break and having them move (or run!) back into that position makes magic.
