Preparing your face:
Start with cleaning your face. Afterwards moisturize your face and lips.
If it is possible, build it into your routine, every day for a week before your photo session.
If your lips are chapped and dry, try using a peeling before moisturising them.
Also clean and moisturize your face and lips 30 minutes before your session.
Preparing your hair:
Wash your hair the night before your session, NOT on the day of your session because freshly washed hair is impossible to style.
Don't change your hair (cut, perm, colour, etc.) two to three weeks before your session, because you have to get used to your new hair first.
Don't spray tan a few days before the session.
Get a magazine you like, look for poses you like and practise them in front of the mirror.
Go through your cupboard and decide which outfits you would like to wear, make sure not to pick pattern heavy pieces.
Patterns distract. Choose single coloured clothing.