Seasonal checklists usually fail by being complete. Thirty items in September is thirty items nobody does. Four items, ordered by what winter will cost you if you skip them, is a Saturday.
In order
Heating first, because it is the one thing you cannot improvise and the only month with appointment availability is this one. Then water: hoses off, exterior faucets drained, anything that can freeze and split. Then gutters, once the leaves are actually down, because doing it early means doing it twice. Then detectors — smoke and carbon monoxide — since the heating season is when CO risk starts.
Everything else can wait
Caulking, weatherstripping, insulation, chimney sweeping: all worth doing, none of them the thing that ruins a February. Do the four, write down what you noticed while you were up there, and let the rest be a list rather than a guilt.