If you are unsure of your stroke type, find a straight line on the ground (ie. the lines in tile or wood) and take your natural stroke with your putter hovering over that line.
If you stay on that line during the stroke, you are straight-back,straight-through.
If your putter goes slightly under that line on the back stroke and then again on the follow through, you are slight arc.
If your putter goes significantly under that line during the stroke, you are a strong arc.
