EXERCISE TO TRY
It is best to take your own photographs for portraits, so that you can achieve some good light and shade in the picture and you can find the angle that works for you. Wait for a bright day and ask a family member or friend if they would help you practise your portrait painting. Take several shots with the light on one side but make sure it doesn’t bleach out the head. As you move around the model watch for how the light catches raised parts of the face. Follow my method of roughly blocking in before slowly refining towards the lighter values