In the winter of 2013-14, the Northern Lights will reach the peak of their 10 year cycle. So if ever there was a time to hit the North of Iceland and search them out, this is it!
Aurora borealis is a natural light phenomenon caused by magnetic particles from the solar wind interacting with the Earth´s atmosphere. Light displays can vary in colour, intensity and movement, with the most typical being a pale fluorescent green. Some people also say you can hear a clapping sound accompanying the lights, which, though refuted, seems to have been confirmed in a recent Finnish study.
Ultimately of course, this is largely a question of chance. You may simply be able to see them from your hotel window on the night you arrive. But to increase your odds, in Húsavík there are dedicated specialists offering tours to find the exact location with the correct cloud cover necessary for viewing.