Pretend the camera is a friend! Also, take a camera and put it on a table or shelf pointing at you and practice. You can also spend time in the mirror trying poses and learn how your body looks at different angles. Do NOT go to the studio alone. Take an adult. And decent professional photographer WILL want you to have a parent with you because they may need forms signed for legal reasons and anyone under 21 cannot sign a legal contract in most states. Some states allowed 18 to sign some types of contracts but no one under 18 can by law. So, a real professional will tell you to bring a parent or guardian. If this guy does not ask, and you tell him you want to bring a parent and he tries to say it is not needed for them to be there...run. Many bad guys hide behind cameras!
It's easy if you feel confident, especially. Try acting natural, like you would around people you're comfortable with. Think about something you like or that's funny. Or even just have someone you love there.
Hi, Refreshme. I had this happen to me when I was about 17. The first 2 days were a nightmare! But then, I learned to look at the camera and pretend it was a person. And after that, nothing was ever the same. All of a sudden the photographer said I became very photogenic and I know I felt a whole lot more comfortable. So I just pretended it was a friend and I even went as far as to name it! It put me so much more at ease. And it's all in being able to relax when it comes to being in front of a camera. If you've got a camera with a self-timer on it, you can practice with it or have a friend of family member work with you. I think this is a wonderful opportunity for you!!!