While it is true that some pretty decent headshots have resulted without the subject of them having done very much to prepare properly; it is also true that with better preparation the headshots might have turned out vastly superior.
Therefore, if you are spending more than chump change to get some headshots done it is probably a good idea to go in with as much preparation as you can.
This preparation would start with consulting with your photographer but generally speaking it's a good idea to:
- Be well rested as there is nothing that can ruin a headshot or portrait more than tired, bloodshot eyes. It may be that this can be corrected with image processing software like photoshop but it takes a lot of extra work that no one likes to do and it likely won't come out looking natural even if it's not a mess.
- Take good care of your skin in the period leading up to a session by avoiding sun and windburns and by keeping it moisturized. An appointment with an aesthetician sometime prior to the shoot day might be a good idea as well.
- If a Makeup artist has been arranged then come to the session with clean, moisturized skin and no makeup.
- If a hairstylist has been arranged then come to the session with clean, dry and conditioned (enough to tame flyaways) hair.
- Stay hydrated but be mindful that too much hydration can result in a slightly bloated appearance
- Have clean, trimmed, unpainted fingernails ... a good manicure sometime before the session is a good idea because the hands may appear in some images and dirty or badly done nails can ruin an otherwise good photo.
- Have your teeth polished and even whitened a little but not too much since whitening teeth can be pretty simple in the retouching stage.
- Work on expressions in the mirror to get acquainted with how different facial expressions feel and look so that you are able to generate the expressions you want for your photos.
- For wardrobe it is best to stick with darker, solid tones as anything else will draw attention away from the face where it should be. Definitely stay away from stripes as they can cause an effect known as moire in photography that can look bizarre and be a real problem.
There may be some other tips preparing for Headshot & Portraits those are the essentials in my opinion.