A portrait photographer understands exposure, the capability of different lenses, light sources, off camera flashes and other light modifiers. The ability to work efficiently on a job, able to quickly adapt to different scenarios in studio and on location is a must.
Gives great posing directions
Nothing makes me happier than when a client tells me " I never thought I can look this good!" As a portrait photographer it is part of my job to give clients great posing directions. Most of us are not models and don't have that natural fluidity in front of the camera. Every single body type has it's sweet spot and a seasoned professional knows how to guide a client there. Posing people in an organic way (having a starting point ) does not mean that the client literally has to freeze into that position.
Makes you look "unposed"
Why work on posing if everyone is wishing to look unposed and spontaneous? What clients perceive as a naturally occurring moment in front of the camera, most of the time is a carefully composed picture by the photographer. Knowing how to pose different body types is essential to hide or accentuate features, by itself it is still not enough to make a great portrait. What ultimately ties everything together is expression.
Gets great expressions from clients
This is actually my favorite part. While posing and lighting are key, in my opinion expression is the most important element of making an image that stands out. I don't want fake smiles and uncomfortable looks in my imagery, neither my clients. Being photographed in a studio surrounded by professional equipment is not what we do on a daily basis. It could make us feel quite shy and uneasy. Since I know that expression makes or break a portrait it is literally my number one mission to make my client feel comfortable in front of the camera. I am genuinely interested in people and starting a conversation comes very easy for me. I let my clients talk and I listen. I never just give directions in a quiet studio, we talk through the entire session and I stay engaged and work at the same time.