I square my top before I quilt, once it is quilted I keep as is.
I have my backing and batting larger than my top, machine sew on my binding and using that seam as a reference trim the back and batt to 1/2". I cut my binding a bit wider at 3" and I like a full binding.
Almost all the time I use French fold continuous bias binding, sew on to the the front by machine, miter the corners, flip and hand stitch down the back.