Actor portraits are shot in the studio, using natural light or studio lights.
To prepare for the headshots, make sure you have had plenty of sleep the night before. You may want to get your hair styled just before the shoot. Tops or shirts should have a small V neck or round neck, or a shirt collar can look good. Neutral colours in light and dark tones, as well as solid blues, greens or browns. Bring a few to choose from and to give variety. Always make sure the clother are ironed - wrinkled tops are virtually unusable.
Think about texture - for example the shirt below:
Headshots on film look dramatic and can have more impact than a regular digital shoot. I aim for it to be more of a portrait than a headshot, with depth of expression and a unique look.