I never took a binding class, taught myself from one of the numerous books I have purchased. I trim top, batting and backing the same. I almost always cut my binding strips 3", fold, then sew a 3/8" seam. I like the look of the wider binding better, even on the smaller projects. I guess if I was binding something that had star points, I'd use a 1/4" width, so I wouln't lose the points, but since there's always a border, I'll go with the 3/8" width Different strokes, I guess.