Well, we have a few Photoshop techniques that may help! However, it does help to ensure your hair and makeup look good (whether professionally or by yourself). Bring your makeup with you so you can reapply if necessary. The best H&S shots are down to the pose and lighting which are adjusted to get you at your best. Be prepared for miniscule movements – the eyes, or head tilt.
Have a think about your jewelry, and earrings. Also, your hands which may end up in the photograph too!