How to photograph faces in the most flattering way
We are all concerned about the way we look, and while we care about how our bodies look, we are especially concerned with our faces. Faces reflect our personality, the eyes more so than anything else. With some practice, you can find the best way to photograph your models face.

First study their features. Most people's faces are not totally symmetrical, especially the older they are. Usually one side is broader and flatter than the other. One side may be longer than the other. One eye may appear bigger. The nose may point one direction or the other. Perhaps there are birthmarks, moles or other distinguishing characteristics. Look at the way the hair is parted -- to the side or middle -- or is it combed backwards.
Have your model look straight at you, then have her turn her face to the left then to the right. Which way looks more flattering to her looks?
Some people say to shoot into the part. Some say to straighten out the nose. Some think its better to put the smaller eye nearer to the camera to make it look bigger and the larger eye farther away. Some say to do the opposite because you expect the eye closer to the camera to look bigger. The same goes with the side of the face that is larger or smaller.
Knowing these things helps give you ideas of how to position the face to try to achieve the most pleasing look, but in the end, what you see in the camera will tell you which way looks best.
Lighting the face is important, too. The side that is larger should receive less light to make it look smaller. Position your light source on the smaller side of the face.
Once you've decided which way you think the model looks best, take that shot. Then take the shots from the other angles you've explored. Put those on your computer and compare them. Show them to your model and see which ones she likes best. In the end, it's what the customer likes and that may be the one you chose -- or not. At least you'll understand how different facial features affect the image and how to set up poses to give options.
With practice, you'll be able to find the most flattering poses and make images that are sure to please your client.