I normally use a 2" strip, press in half and use a 1/4" seam allowance. I sew to the back first and fold over to the front of the quilt. My bindings are very narrow and I try to make them so they don't take away from the quilt top.
When using a 2-1/2 inch binding, I use a 3/8 inch seam allowance.
When using a 2-1/4 inch binding, I use a 1/4 inch seam allowance.
Nice thing is that there are no "Quilt Police". Find what you like best and run with it. It will be beautiful.