I used to pin, but I don't anymore. I use 505 spray (love that stuff!).
I lay my batting out, then my top on top of it, smooth it all out and make sure it's square. Then I fold back one side to the center, spray the batting, and carefully smooth the quilt top back down. Rinse and repeat for the other half.
I will then "baste" the major outlines (borders and blocks) if I'm going to embroider.
If it's a simple quilt, I spray baste the backingon in the same matter, and stabilize the quilt by basting the borders and blocks, then quilt as usual.