Though headshots are pretty painless even to the person that hates having their photo taken, there are some things to think about when having your headshots done.
Wear minimal jewelry. Now, there are exceptions to this, like if you're having dramatic portraits taken for a specific reason, but for your typical corporate headshot, you want to keep distractions to a minimum. Large earrings and necklace will only take away from your smiling face.
Keep makeup natural. Wear your makeup just like you would to the office. Perhaps you could punch up your lipstick some for a brighter look, but no over-the-top lipsticks, eyeshadows, etc.
Make sure your hair looks neat. I think this one is a given. You don't want to show up for your headshots looking like you just rolled out of bed. Brush your hair and wear it like you normally would to the office. It doesn't have to be fancy.
Wear solid-colored clothing. Just like with too much jewelry, you don't want to distract with loud prints and/or colors. For men and women both, you want to wear a solid shirt or blouse, and it's your choice whether you wear a jacket or blazer, though they do look very nice in the photo.
Headshots are chest up. Headshots are just that - head shots. The focus should be on your face with good lighting and no shadows.
You should be looking directly at the camera. Eye contact is important, so for a professional headshot, you want to make sure you aren't looking off to the side or anywhere else. That becomes a different portrait.
Headshots should be you. Your photo should look like you do in real life, and it's important to have updated headshots every couple years!
A professional photographer should always help you with your corporate headshots. You want to look professional, too!
I offer 10-15 minutes of shooting for headshot sessions. It's so quick and easy, and I help you the whole time.