Northern Lights Tromso

I'll be heading to Tromso in the hope of seeing the Northern Lights in November, December or January. Can anyone give advice on which month may be any better/worse for either seeing the lights or any other reason - weather, activities, festivals etc.... Also, in my NL research, the biggest thing seems to be the issue of cloud cover and snow. Are any months better for clear skies? I won't be expecting to see them in Tromso City itself (although that woud be a welcome bonus!), and I plan to head out on a tour each night (4- 5 nights), so would cloud cover be a problem then, or can the guides simply keep travelling to find clear skies? Also, would any one recommend (for or against) a cruise/dog sled/reindeer tour to chase the lights? I thought a combination of these would be an option so that if the Lights don't appear, at least I won't just be driving around in a bus every night. Of course, and other advice or suggestions would be most appreciated.
Thanks all!