It depends on the quilt. For smaller quilts, I will use a 2 1/4, double folded. If it's for a baby or toddler (or child), I will either sew it to the front, and then SITD on the back. Or I'll sew it to the back and anchor it with a decorative stitch to the front. Kids quilts need to be plenty strong, so I don't hand quilt. For regular quilts, I'll stitch it down the front, and hand stitch the back. The bigger the quilt, the wider the binding. I'll use 2 1/2", double folded for doubles and Queens, and I've been known to go up to 3" for King's. Either that, or I'll use a very narrow binding, depending on the needs of the quilt, and how much I want the binding to show. I've gone as low as 1 1/4 inches, double folded, so it's almost a piping, if that's the look I'm after. Those are harder, and I almost always SITD because they really need to be stitched securely.
So that nails it down to no one particular way, doesn't it! Overall, the bigger the quilt, the bigger the binding, unless I don't want any attention drawn to the binding, and then I'll use a narrow binding just to finish the quilt.
Hope that's clear as mud!
Cheers!