1) Base Layers
It is extremely important to have a tighter shirt that is a bit lighter as your base layer with any outfit in a cold destination. If you just wear a warm sweater, the heat may escape your body still if you don't have something tighter under it to keep in the heat within your body. Base layers can be a light long sleeve shirt or even a tighter short sleeve shirt that you can wear under your sweaters.
2) Pack Boots, Not Shoes
It's best to pack one pair of boots that you'll be able to wear pretty much everyday in your destination and then another paid of nicer boots you can pack for going out at night, if that's part of your travel plans. I believe those are all the footwear you need to pack, and you will also be wearing one more pair of shoes to your destination, so pick those wisely as well.
3) Warm Accessories
Pack accessories like gloves, hats/toques, scarves, long socks, which gives you some extra protection from the cold and adds something a little extra to your outfits. Try and pick these accessories that will go with most of your outfits that you packed so everything goes together nicely.
4) Big Coat
Choose your big coat very carefully. Make sure it is the right colour to match everything else you've brought, and also make sure that it will truly keep you warm and that you can move around in it!
5) Fleeced-Lined Leggings
These are life-savers! You can wear a warmer dress with these leggings underneath to keep you warm and they are also really comfy if you are planning on doing a lot of walking one day.
6) Only the Essentials
Since you are packing lots of layers and puffy coats, it can be difficult to fit all of it in your suitcase! So, you need to make extra sure you are only packing stuff that you will for sure plan on wearing in your destination.