Truth be told I've worked with some photographers whose amazing personalities make me melt to butter and laugh constantly, but I am simply not one of those people! I have devised a list (evil plan at work) that seems to work >=D. (And not in any particular order)
1. Build a rapport with your client before you ever pick up your camera.
Pre-consultations are so important! I always tell my clients we should meet before they even hire me to make sure they are going to be comfortable being photographed by me! My personality isn't for everyone and I know when to let a client go. When they come in, I want to get to know my client so I can stop thinking of them as just "client" and know them by name. I always feel like I've made a new friend by the time my clients leave the studio!
One of my favorite things to do is to look at the back of the camera. A total faux pas, I learned that in school, I know. I've shot film though - I've paid my dues (maybe not as long as some photographers) - and I've earned it. As I get more excited, the energy keeps pumping up and my clients are dying to see an image. You know that image that's just 'The shot'? I show that to them. After that, it's cake the rest of the day because my client trusts me. They know how great they look (without retouching) and feel amazing!
3. Always have someone with you on the day of the shoot
Their friends don't count. Have a female makeup artist or assistant there to help you out.
4. Always ask permission before you touch.
I know I've heard this argument back and forth - Ask or don't ask and just be confident and do it, but as a model I always felt more comfortable with a mixture of both. Ask permission with confidence. Don't come up to a girl and start arranging her hair or bra strap without talking to her. Really? How would you feel it someone randomly came up to you in your personal space and started arranging your clothing?
5. Don't shoot first and "Retouch it out" or "delete the bad images" later
As a model, I heard that from photographers all the time. Example One: I hate it when my hair gets all flat. I have a huge head of hair and it becomes a mess quite easy. If I say that, keep an eye on it! Example Two: I would be wearing an omega push up bra trying to attempt some form of cleavage and a little bit would show too much. Example Three: I'd be doing implied nudes and whatever was covering me would fall slightly out of place. The photographer would keep shooting and when I noticed they would say, "Oh, I'll just photoshop it out". or "I won't use the ones that show too much". How freaking creepy is that? I'm going to go home and wonder what they are doing with the unretouched/nude version. If I were someone with a prestigious (aka not an artist) job, I wouldn't want that version of me in digital form at all!
That sort of rolls into:
6. Show them the shots you do (Similar to 2, but for a different reason)
When doing implied, (or any images really) show them the images to prove you aren't shooting anything that shows anything and to make them feel comfortable. If you accidentally happened to capture something they don't like (pay attention and try not to), delete it immediately in front of your client.
7. Show poses even if they feel silly.
Have you had that client that just couldn't get that pose no matter how much you tried to guide them? Mirroring is one of the easiest ways for someone to get into a pose. If you feel silly doing the pose - why would your client do the pose? Practice your favorite poses in the mirror before showing them to your clients. If you're a guy, this works even better because it's really amusing watching a guy do them.
8. Let your clients know when they are doing great (and be honest)
9. Compliment their best features
Again, BE HONEST. Every single woman is absolutely beautiful. If you can't see it and are just snapping photos for a paycheck, why are you a photographer?
You know how they say Laughter is the best medicine? Have genuine fun. Love what you do. Shake it out, loosen up, and get back to it. I can be very serious myself during a shoot because I need to control the poses to move their bodies to showcase my client's curves the best I can. Don't forget laughter is contagious!
If all else fails, hire a makeup artist or an assistant that is either relaxing or funny! One of my good friends has a very dry sense of humor (which works for me since I like dry humor) but when we used to work together he had a very goofy assistant that I also had tons of fun with.