9 ways to prepare your home for winter
Prevent ice dams on the roof
Seal air leaks. Shutting down air leakage is probably going to have the biggest effect, and it's the kind of thing you can do incrementally. The second would be adding insulation. If you have R18 insulation value, turn it into R36. This is where your energy audit will be helpful.
And the third is making sure your roof is vented properly, if your house is designed to have a vented roof. Make sure your soffit vents aren't blocked, your gable vents are open.