During the session, do everything you can to gain the trust of your subject. Even if everything on them looks perfect, fix stray hairs even if you don't see any. Adjust coat jackets and ties, even if they look fine.
Talk to them...I repeat, TALK TO THEM! You're a stranger and they'll likely be very reserved around you (especially high school seniors) so it is your job to make them feel at ease with the camera and in essence, you. If you can get them to talk about themselves then you've done a great job. Who doesn't like to talk about themselves? It's all about finding common ground with them.
When I adjust a pose, I like to explain (in simple terms) why I am having them pose that way. After tilting a head a certain way, I might say, "This is going to give more curvature to your body, which is always a good thing in a portrait and it will make you look beautiful." Just something that they'll understand and be less nervous about doing. Put yourself in their position--they don't want to be there 99% of the time so you have to get them to warm up to you. In the end, if they enjoyed your personality, they'll love the portraits that much more, even before seeing them. You are selling your photographs even before you sit down with them a week later in a projection room, proof room, etc. etc. The more they enjoy you, the better they'll look and the more they'll buy.
Compliment the subject. They feel weird doing the things we ask them so you must assure them that you know what you're doing and that they're going to look great. For girls, I like to use words like beautiful, gorgeous, elegant, graceful, etc. to let them know how they look. Just saying, "This makes you look pretty" almost sounds amateur don't you think? Women want to look beautiful, graceful, elegant, etc. so why not tell them they are? For men I use words that they associate more with as well. ie: cool, nice, excellent, slick, etc. etc. It can vary by the age of the subject.
I myself have always loved to laugh and joke around. I like to associate myself with people who are like me in that regard. My sense of humor is my greatest quality in my opinion. Unfortunately, not everyone out there wants to joke around when I do so when someone comes to be photographed and I can tell they are not the laughable type, I still make it an effort to make them comfortable but moreso by being polite and freindly and professional. I'll still pop off a few jokes here and there but nothing with the goal of getting a huge laugh-just a way to get me to smile a little bit. Dry people are my biggest challenge to work with so I have to keep myself...myself. If that makes sense...probably doesn't but oh well.
