Fall maintenance is really winter preparation. The tasks you do now prevent the frozen pipes, heating failures, and ice-dam leaks that strike in the dead of winter.
Heating
Service the furnace and replace the filter before the heating season peaks. Test the thermostat and detectors, and reverse ceiling fans to push warm air down.
Water and drafts
Shut off and drain outdoor taps, disconnect hoses, and insulate exposed pipes. Weatherstrip and caulk drafts around doors and windows to keep heat in.
Gutters and grounds
Clean gutters after the leaves drop so meltwater drains and ice dams are less likely. Trim branches that could break under snow, and store or cover outdoor furniture and equipment.