We use all sorts of nonverbal signals that help to communicate our attitudes and feelings to other people. This is one reason why written communication can be harder to interpret than verbal, in-person communication. Some examples of signals include:
Paralinguistics. These are aspects of our speech that are separate from the words we use and are, therefore, nonverbal. So, for example, the volume of our voices, or the tone of our words can convey a great deal about our attitudes.
Posture. This sends strong signals about our attitude towards the speaker and/or the subject being discussed. For example, if I listen to you with my elbow on my desk, my chin in my hand, and my eyes looking down at the desk, you are likely to infer from my posture that I am not very interested in what you say. If, by contrast, I lean forward towards you and look directly at you, you are likely to infer (if you are American or from a similar culture) that I am interested in what you are saying.
Gestures. Gestures can often help to convey messages about our attitudes. For example, if I accompany some critique of your work with strong slashing movements of my hands, I can send a more aggressive message to you than if I leave my hands relatively quiet.
There are, of course, many more signals that we can send. However, these are a few of the more important ways in which we convey meaning through means other than words.