Adding bangs to a hairstyle can make the forehead look considerably smaller. Celebrities like Tyra Banks have, on occasion, chosen this style to conceal the extra space and achieve greater balance in their face shape.
While various types of bangs exist, a specific type that can narrow the forehead are longer, side-swept bangs. "InStyle" magazine also recommends side-swept bangs and, more specifically, a version of it called swingy bangs, described as "heavy side-swept bangs that start in the center of the forehead and taper diagonally to a cheek-grazing length."
Men with large foreheads, however, should let some of their hair fall onto their foreheads. An example of this style is Johnny Depp in the movie "Public Enemies."