What is correct photoshopping and what is incorrect photoshopping of Headshots? Truthfully, you don't want to overphotoshop a headshot, especially an actor headshot. Remember that the goal of a Headshot is to show you how you really look but without distracting elements. Therefore, it is best to only take out the distracting elements, while leaving everything else mostly the same.
The four main things to worry about when it comes to photoshopping images are:
Bags under the eyes. Bags can easily be covered by makeup in a film or play, so there is no reason to keep them in a headshot. Having or not having bags under the eyes doesn't make a difference in the expression and character, so you should remove them.
Distracting facial marks.remove pimples and other facial distractions that will make the client happy. Remember that certain facial features can't be covered by makeup, and others give the person more character. Leave those.
Skin shine. Remove shininess from the skin of he clients your are shooting. Try to do this during the shoot by bringing powder or a napkin to keep the face dry. If you have to remove it in photoshop, it's fairly easy to do, and definitely should be done.
Teeth whitening. Don't whiten teeth so much that they look fake. But remember that instant teeth whiteners make it easy to fix someone's teeth right before a film shoot, therefore you can definitely whiten someone's teeth so that they look more attractive.
Brighten the eyes. Use the dodge tool in photoshop to whiten up the teeth of the headshot client just a bit. Doing this will make them stand out a bit from a lot of the other Headshots. Remember that a headhot is all in the eyes. Just don't brighten the eyes so much that the photo looks fake!