There are three basic knots -- think of them as small, medium and large. Your collar type dictates the one to wear. The bulkiest is a full Windsor, a fist-size knot often seen around the neck of Diddy. The Windsor and its little brother, the half Windsor, are both well suited to a spread-collar shirt able to showcase the knot's heft. For most occasions and shirt collars, however, the standard four-in-hand -- the smallest knot -- is the best plan.