Refining a specular highlight is a lot more challenging than refining a shadow – not that shadows are easy. The primary considerations for shadows are your reflectors, secondary light sources, distance of primary light source, and subject tone. Specular highlights are all that and more, but the reflective quality of your subject also plays a huge role. It is very common for us to photograph subjects that have numerous different surface qualities in a single image – clothed people with jewelry are good examples of this. While you are busy lighting your diffused highlights and shadows to perfection, your subject is busy reflecting specular highlights all over the place that demand equal attention!
Somewhere in this website I recall writing that the diffused highlight is your cake, and the shadows and specular highlights are the icing. This tutorial will help you learn how to spread that icing like a pro!