Tips for Great Professional Headshots

A few days before the business headshot photoshoot

Rest and Hydration. Get lots of sleep and drink plenty of water for several days before your shoot. Avoid excessive alcohol intake.
Plan Your Wardrobe. Start a week in advance. Plan to be the best dressed in your industry. Check your outfit and make sure it fits well and is cleaned and pressed. Avoid shiny fabric and keep jewelry to a minimum. Avoid makeup with glitter or shiny elements.
Glasses. If you wear glasses, do they have a non-reflective coating? If not, consider not wearing them or have your optician remove the lenses for the shoot and just wear the frames.

Be Ready with your Outfit. Follow the above and your outfit should be all set.
Practice Posing. Look at headshots online and find ones you like. Talk to your photographer ahead of time. Look in the mirror and practice. Your photographer will assist you further when you get to the session.
Relax and Have Fun. Take a deep breath and enjoy the headshot session.