The Northern Lights by Boat tour from Special Tours was recommended to be by fellow passengers on another tour I was doing in Iceland. Their website made it easy to book via my mobile phone. The pickup from the hotel was on time, and once I arrived at the boat, I was given the option to wear one of Special Tours's cold weather suits over my clothes. The boat had an outside viewing deck as well as an inside, heated cabin with a cafe.
The guide told us what settings to use for our cameras, and informed us that as we were leaving the harbor, the Lights could already be spotted in the sky. This led to an incredible display that lasted the entire time we were out there, about 2.5 hours. In addition, the guide offered to take photos of any passengers with the aurora in the background, which were then posted on line the following day.
Obviously, the company cannot guarantee whether the Northern Lights will be visible, but they do an excellent job getting you out there, away from the lights of the city, and do whatever they can to make it a memorable experience.