A simple and effective technique for "focusing" attention on a portrait subject (pun intended, LOL) is to frame the person in some natural way, either with other people, plants, furniture, etc. I like this little trick and use it often in what I call "orchestrated candids", where I set up a situation so my subject is comfortable and let them interact with others while I'm off a ways shooting with a 200mm f2.8 lens. This works great in natural light or when using a constant light source as strobes become too obvious. One catch, be prepared to shoot a lot of frames as the delete rate is high due to odd expressions and closed eyes.
One of an "orchestrated candid" portrait series shot for a Wall Street client