The traditional advice for seeing the Aurora Borealis involves picking a time well in advance and then staying there for a week or more and hoping for the best.
However, if your schedule permits, there's an alternate approach that few people know. You can guarantee a good show by waiting until there is a serious solar storm / coronal mass ejection (and clear skies and a new moon) and then racing to get to the arctic before it does. I proposed this approach a while ago, and many friends have tried it since then, always with success.
Here's a brief slideshow that explains it.