Study the features of the five basic universal emotions of anger, fear, disgust, sadness and happiness. Practise them in front of a mirror. There are countless emotions but, like hues derived from primary colors, they are a blend of basic emotions.
Look into the eyes for dilating pupils and rapid blinking. Both are signs of attraction, but rapid blinking can also mean the person is being evasive.
Note the movement of eyebrows, whether they narrow in anger, are raised in surprise or come together in sadness.
Observe the wrinkles on the face. Remember that anger causes wrinkles on the forehead and a wrinkled nose is a universal sign of disgust. Similarly, a sure sign of a true smile are wrinkles at the corner of the eyes ( like crow's feet), but a fake smile leaves the eye muscles alone.
Watch out for "micro-expressions", the fleeting expressions that last up to a tenth of a second. Micro-expressions, if they do not match the dominant expression of the face, give away how a person truly feels.
Turn off the sound when watching TV. Observe the length and formation of facial expressions, giving particular attention to eyes, eyebrows, lips and wrinkles. Try to identify how the person feels based on your reading of facial expressions on the screen.