Besides activity from the sun, two factors will maximize your chances to see auroras: clear skies and darkness. In Northern Europe nights are dark mostly between September and March. During the last week of August and half of April it can be possible to see auroras, but the time each night is very short. So if you are travelling to mainly see the lights, I’d say September – March.
Near both equinoxes (September/October and Feb/March) the skies are usually the clearest. Between November and January is the darkest time, offering very long nights.
The Moon phases will affect your aurora experience as well. A Full Moon is naturally bright and therefore overpowers some details and weaker colors in the auroras, but at the same time it lightens up the surrounding landscape which is very special. New Moon reveals most details of auroras and there will be plenty of stars in the sky. First and last quarter (half the Moon visible) are a good mix of everything.

Here some examples of different moon light:

In Northern Europe there are many places where it’s possible to see auroras. Northern Finland, all of Iceland, Northern Norway and Northern Sweden are all great places within or at the edge of the auroral oval. Choosing between these is a matter of preference, I’ll leave that to you.
A good decision maker for a travel destination are the Kp-lines of the  Kp-index maps from NOAA (Eurasia and North America). Being somewhere near the Kp=3 line will give you a good chance to see auroras near the horizon towards North-West and a fair chance to see them dancing above you. If you go a few hundred kilometers North your chances drastically increase to see auroras dancing all around you, because you are entering the Kp=2…1 zone.
Remember, strong geomagnetic activity (high Kp-value) occurs less frequent than weaker activity.

Make sure you have the right clothing for the season and check out the weather forecast for your destination. Nothing is worse than seeing great auroras and having to leave because you are getting too cold.
For winter, it’s all about layers. Start off with one (or more) woolen layer, Merino wool is excellent but other wool will do as well. Fleece over that usually works well and all can be topped off with a winter jacket and trousers, best for them will be windproof.  Shoes and gloves will be also essential as your toes and fingers will be one of the biggest challenge to keep warm. Hand and toe warmers can get easily purchased online. If you do not have special winter wear, you can usually borrow warm overalls and thick shoes from a local snowmobile tour company for a small fee. Search online and contact them.
Oh, and make sure to properly protect your hear and ears against the cold as well.
Autum nights are usually not as cold, but being outside for longer times you better to be prepared. Jeans, sneakers and a autumn jacket will not be enough!

Other than clothing, it is good to bring:
– thermos bottle for hot juice, tea or coffee to keep you warm
– balaclava (a ski mask to protect your face)
– a flashlight or head lamp with full batteries

Some of you most likely want to know about photo gear. That is covered in part 4 of this guide.

In case you are on your own, not participating any aurora tour, your first tasks will be to find a good viewing spot with two main goals: a wide view and little to no light pollution. If you stay in a cabin away from a village you will not have to worry about light pollution. Find a lake or a field where you have a good, wide view. In case you are right in a village where are a lot of street lamps, I suggest you use the daytime to look for potential spots. In winter, frozen lakes are an excellent. Artifical light like street lamps have two effects. When you are close to them, you will not see as much of the aurora. They are also often the reason for orange snow or clouds in photos.
When auroras suddenly appear you want to be ready knowing where to go. It is also possible to use an online map service already before your trip.
For me personally, I enjoy exploring the areas and finding new spots. That is only when I am alone out there. The locations during my workshops and tours, I know well.

Do not forget to
– bring your fully charged batteries for your phone, camera etc. Charge them in the afternoon. In cold temperatures batteries will discharge faster.
– pack your flashlight / head lamp
– the protection for head, ears and hands.
– take your keys!