Emotions are expressed by players either by entering an emote into the chat window or when a direction key is pressed.
Using the arrow keys to trigger emotions. Up is for happy, down for sad, left for scared, and right for angry. While in a party the emotions are also shown in the Party Window. Different combinations of emotions can be triggered by typing in a certain chat phrase, or by holding SHIFT or ALT while pressing a directional key.
Entering certain emotes into the chat box will trigger the player's character to express themselves as well. Here are the emotes which trigger each emotional response.