On my blog you can find the latest aurora forecasts, based on reading forecasts from several places. Please note that my forecasts do not guarantee your success in aurora hunting, but I always strive to deliver reliable information that I gather from several sites.
Predicting aurora activity is serious science that requires monitoring activity on the sun. When the earth-facing side of the sun erupts, scientist can predict how long it will take for the plasma to travel to earths atmosphere. But for real enthusiasts you can do some observations yourself. Just remember to never ever look at the sun directly through any kind of magnifying glass (binoculars, telescopes, camera lenses etc.) at all.
There are several places on the internet that interpret this information and publish both long term and short term predictions for auroral activity. If you are preparing a northern lights hunt, checking some of these pages here can be very useful. Gedds, TV2, or Forecasts for Canada.
But since auroral activity is not the only factor in determening wether or not you will be succsessful in finding the aurora you might want also want to check out if there will be openings or if it will be fully overcast. In that case the Icelandic Met Office can be very useful.