I sew a 3/8" seam for binding and normally don't do anything prior to sewing on my binding. Although, my quilt w/ wool binding, which is puffier than cotton binding, I did find sewing 1/4" and then sew my binding on was helpful.
This is a magnetic seam guide that i use and it helps me keep a straight(er) 1/4" seam. I got mine at JoAnn's.
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