I do nothing different in winter except a longer warm up.
I run middle grade fuel. Every 4th or 5th tank, I fill with high grade and an once of seafoam to keep the carb clean.
I have a normal NGK cr7hsa plug.
I run Rotela T6 5w-40 synthetic oil.
I've never used a battery tender once in almost 2 years, and never had a battery issue. Starts right up, even at 5F last winter.
I don't have a garage, so only a bike cover keeps the snow off.
I just ride all year and the scoot never sits longer than a couple days at a time.
My Super8 150 is a tough little beast!!
Duke-