Geosight #1: The aurora
Although aurorae are visible far from the polar regions (real biggies have been seen in distinctly unpolar spots such as Hawaii), places such as Scandinavia, southern New Zealand and Alaska are favoured for viewing them. But don't go too far north or south. The region inside the annulus is rather poor as an aurora-watching zone. You'll see more of them a few thousand kilometres from the pole than you would at the pole itself.
Once you get there, the rules are simple enough: pick a time when the Sun is lively, and look upwards at night.
However, this is trickier than it sounds. For one thing, it is not for nothing that the polar regions are known as the Land of the Midnight Sun. In the summer, it is light most of the time. And the summer is the time when it is easiest to get to the far north or south, and when the temperatures are at their most acceptable.
Next, the aurora is a light in the sky. So you need a site where it has as little competition as possible. Somewhere dark and far from a major conurbation is ideal. You also need to choose a night as near as you can to the new moon, as a full moon will flood the sky with light. These are also the criteria for a good meteor-watching site so you may be able to spot both of these upper-atmosphere treats on the one visit.
Finally, you need the Sun to be active. The big flares that drive major aurorae are not predictable. But like sunspots, they go in an 11-year cycle (to be exact, a two-peak 22-year cycle) that last topped out in 2000.