before scheduling
Don't get your hair cut or styled in the days before your shoot - most hair dressers and stylists cut hair so that it looks its best 1-2 weeks later. If you do get it styled, make sure your stylist understands when your shoot is.
before the shoot
Start thinking about poses and styles prior to the shoot, feel free
to communicate any ideas you have to the photographer. Whatever
photographer you choose, it is likely they're just meeting you for
the first time, you likely have a much better initial idea what
looks are best for you.
Don't skip meals the day of and drink plenty of fluids, both hunger
and thirst can have quite visible effect on the final photos.
No drugs or alcohol to "loosen up." Both can have negative and
visible effect on photographs, and often can lead to communication
difficulties with the photographer. Be cautious the night before
as well, as hangovers are rarely attractive. ;)
Women, pay particular attention to any unwanted hair, particularly
around the lip.
Men, if you're unsure if you want to go with a clean-shaven or rough
look, speak to your photographer and make sure they leave time to
shave halfway through.
makeup
Keep in mind that cameras pick up everything. Makeup is really a
double-edged sword. A camera will pick out skin blemishes or
discolouration, but will just as easily show uneven blush, or sharp
lines in eye shadow. If you're not using a make-up artist,
simplicity may be key.
Men, for most this is a dirty word for use on themselves. However,
a base cream or powder will minimise shine on the skin, allowing
for much more natural-looking photographs. Have someone help you
pick out the right one for your skin tone, and show you how to
apply it. The aim is to look like you are not wearing anything, yet
not reflect back the studio lights.
Both for men and for women who would prefer not to wear lipstick,
grab some cherry chapstick. Don't mix it up with lip gloss!
clothing / wardrobe
Avoid bold patterns, as they will be amplified by the camera and
distract from you.
Be aware of colour choices, you know what looks best on you,
although again, pay attention that it isn't something that will
distract from you.
Have a couple different outfits laid out, two or three should keep
your options open and give you a couple distinct looks for your
photos.
Watch out for wrinkles, as these have a tendancy to stand out on
camera.
Avoid clothing that you know feels weird or is uncomfortable, many
times this will lead to you showing that feeling on camera as
well.
during the shoot
Most important of all, communicate witn the photographer. Not only
for changing positions or poses, speak up if you need anything, if
you're uncomfortable or if you have any kind of problem at all.
Speak up if you have ideas! You have much more experience as to what
looks good on you, or photo ideas that have worked in the past.