Photographers can run in situations where it's difficult to make their subjects feel comfortable and relaxed when they are photographed. The first step is all about being prepared. Let them know what the shoot will be like. I always suggest my clients find clothing that really reflects their style, personality, and taste. I also suggest they choose outfits they are comfortable in and that look great on them.
I learn if there are things they don't like about themselves so I can work the right angles. It can be a bit scary to just jump into a photo shoot unaware of how to pose. It's helpful to direct clients to general poses and then allow them the freedom to become more comfortable and make the pose their own
The day of the shoot, I try to start in my office and chat a bit to get them comfortable before we head into the studio. At that point, I really just make a fool of myself until they laugh, anything to keep it light. It's important to engage with your clients on more than just a “photographer-subject” exchange. I chat through the whole shoot so they can take their mind off being photographed.
I assure them I love how things are looking. It's nice to notice and compliment your client because they took the effort to get dressed up. This will make the clients feel more confident in themselves and they will definitely come through in photographs. I never have a problem when I establish a friendly relationship and keep the conversation going!