I shoot people. I LOVE to shoot people.
... of course not literally, but with my camera. For me the key to outstanding people photography is to create a connection between the subject and the viewer. 
I have to connect to my model in the first place, because I am the viewer at that moment when it clicks. If we have a connection the viewer will have it, too. 
Connection means emotions and in headshot photography these hardly come naturally. They have to be teased out and at the same time unwanted or faked emotions have to be avoided. 
So good headshot photography is very little about technique and all about communication. As Peter Hurley says: "As a headshot photographer I am 10% photographer and 90% therapist."