Practice Makes the master

The first and usual method for the novice photographer is trial-and-error. After having taken someone’s picture for your first attempt at a portrait, you look at it and realize it could be improved if the subject didn’t, say, look so unexpressive. The person may be just standing there. So you have another go at it, and take another picture, asking the same subject to perhaps lean against a tree and tilt his or her head, and the resulting picture is improved.