Some of the most common problems I've encountered so far with portraiture shoots, are overcoming adult anxieties. Things like "I'm worried the kids won't behave" and "I hope the dogs don't run off" are normal worries, when you're paying good money for a photo shoot. However, the one that tops all of those is "I'm not very photogenic and I hate having my picture taken."
I think 90% of bookings I've taken so far, has started with this particular statement and I for one can totally understand. The problem with us adults is, we have grown to dislike certain parts of our bodies over a period of time and unfortunately, it is those particular hangups that jump out and shout "LOOK AT ME" when we view photos of ourselves.
For me it's my chins! No matter how much people say "oh what a lovely photo" I'm sat there thinking, "Oh my goodness, where has my jaw gone?" I can assure you that we are the only ones that see these imperfections. Everyone else takes the photo at face value, they take in the surroundings and the subjects as a whole.
The key to a perfect photo shoot, is to find a photographer that puts you at ease. Choose someone who works naturally outdoors, where you can be yourself in somewhere you feel most comfortable. Someone who isn't sticking a camera close up to your face, but using a zoom that can capture you from afar. Also, if you are self conscious, I would suggest steering clear of studios where you are being told how to pose.