Avoid busy and small prints. Neutral colors are preferred and recommended.
If your headshots are for professional use dress accordingly with attention to fresh collars and pressed jackets. Likewise, if you are shooting for Agency have multiple options of non distracting items available.
Be photo ready when you arrive on site in full hair in makeup. Corrections will be done in post production but arriving at your best guarantees the best final images possible. Have wardrobe options and accessories readily available.
I cannot stress highly enough the importance of bringing an assistant for on site adjustments for hair, makeup and wardrobe! Mua's can be recommended upon request but a friend will do.
Shooting is fun! And overly posed photos can look stiff and unnatural. Practice a few poses before the shoot and feel free to move and breathe organically, then leave the rest to me!