The feet tell all
More interesting research has shown that in a lot of cases, people will point their feet away from someone if they want to end a conversation. If they want the conversation to continue, their feet will be pointed toward the person they are talking to at that moment. So make sure you give the feet a few glances.
By checking on the feet, you can tell whether or not someone is actually interested in chatting with you or just can not wait to leave. Do not take it personally though, it could also mean that they have something else on their minds or they are just in a hurry.