To prevent puckers on the back when you machine quilt, I highly recommend *heavily* starching the backing before you layer. I mix a 1:1 solution of Sta-Flo liquid laundry starch and water, apply to the fabric using a large wall painting brush (very fast and easy), wait a couple of minutes to make sure the fabric fibers have absorbed the starch, toss in the dryer, then iron with steam. This stiffens and stabilizes the backing so it is unlikely to bunch up or pucker while you are maneuvering the quilt under the arm of the machine.
It's a good idea to also use a few layers of spray starch on the top -- again, to stabilize the top. You would know at that point if it's not going to lie flat. When a top doesn't lie flat, it can help to use a medium loft batting (such as Hobbs 80/20 or Hobbs Polydown), keeping your quilting lines a little farther apart.
I also recommend using Elmer's glue for the basting process.