As a sketcher, you could be forgiven for thinking that drawing expressive people is all about the face. But an expression is worn on the body as much as on the face. Shoulders slump or are high and tense. Heads are held high or tilted quizzically. Body language tells you much about what a person is feeling.
Practice, from life, makes perfect. Photos don’t give you the necessary three-dimensionality you need nor the pressure that will force you to cut to the chase.
While my counsel is always to draw what you see, sometimes a little pre-acquired knowledge about proportions and relative sizes of parts of the body can come in handy.