Think about the word or feeling you are going to express and if the feeling is positive, negative, affectionate or full of another emotion. How the sign is interpreted by the person receiving the message is very important.
Decide if the motion will be performed using flowing delicate moves or if the emotion demands forceful gestures. A gentle movement will express kindness or affection while a more bold move will express intensity.
Use facial expression, especially incorporating your eyesbrows, to help convey the message. If the sign or feeling is mad, let your face show the anger. If you want to express happiness or affection, soften your expression and smile while signing.
Incorporate your whole body in the sign. If you are feeling mad, your body may be more rigid and the sign performed closer to your body. If you are outwardly angry, your gestures will be using the space around your body to tell the level of anger that is being felt.
Speed up the motion of the movement of the sign to help express the degree of an emotion. When people talk, words come out faster and faster the more excited or upset they are. The same idea works with signing.