Here are some simple and basic tips for you:
1. Turn your furnace on now to make sure it is working. Better to know now if you need service.
2. Think about having your furnace professionally serviced prior to winter. Your furnace will operate more efficiently, saving you money.
3. Inspect your filter. The filter should be free of dust and debris. If the filter is dirty, replace it. Bring your old filter to the store so you purchase the right sized filter.
Here is a short video with more information: Prepare Your Furnace for Winter