At some point, even the most stimulating conversation begins to lose its "flavour." The last thing you want to do in an interview is belabour a point.

If you sense that an interviewer is becoming bored - he or she is losing eye contact with you or rustling papers - you need to change topics in order to regain his or her attention.

You could ask them a question, such as whether they agree with something or not. This tactic allows them to move on with the interview without feeling as though they have cut you off in mid-sentence.