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.