Put Your AC to Bed
Prevent clogs and discourage pests by rinsing away the dirt and grime that's accumulated on your AC unit. Also remove leaves, branches and other debris from the surrounding area. Inspect the system for damage and then cover the exposed pipe with foam insulation; this will prevent freezing.
Finally, you'll want to cover the unit but not entirely, as this could lead to moisture problems. Use a specially designed AC cover, or simply place a piece of plywood on top of the unit to keep out the winter weather and debris.
Fine-Tune Your Furnace
Schedule a service call with a heating professional now. If you wait until heating season is in full swing, you may find it difficult to get on a contractor's busy schedule. A furnace checkup will include a review of your thermostat settings, an inspection of controls and drains, a tightening of electrical connections, and the lubrication of moving parts.
Go the Extra Mile
Now that your system is ready, keep your furnace running its best by changing the filter regularly, typically every month. Identify areas of your home where warm air might escape and seal them appropriately. Caulk leaky windows and doors, and seal gaps around chimneys and recessed lights in insulated ceilings.