I do not pin when sewing binding to quilt edge. One thing I do that is a little unusual is that I do not cut the quilt edge before sewing on binding; I simply mark the cut edge with a black Sharpie and use that as my "virtual edge" when sewing on the binding. I find that this method ensures that the quilt edge remains flat and undistorted while I am sewing. I am *very* careful to trim the quilt edge after the binding is sewn on; the one thing you do not want to do is trim any of the binding at the corners (you will have a hole in your binding when you turn it!).
I need to backtrack and mention that I do a very rough pinning of binding to quilt before I start sewing. This is to make sure that any binding seams do not fall right at a corner. This gives me a good starting point for the binding. An alternative to doing this is simply to stop and adjust the binding join when you see it is going to fall at a corner; just undo the join, cut off a few inches, and re-join.
After getting the binding on and trimming the quilt edge to match, I iron the binding away from the quilt. This step helps me to get an even turn on the binding.
Another extra step I do (not necessary if your last step is hand sewing the binding on) is take the quilt to the ironing board and use Elmer's white washable school glue to turn the binding and glue it in place with my iron. This helps me get the binding to completely cover the original stitching line without going over too much. I then use a decorative stitch on my sewing machine for the final sewing.