There are only two major rules for furnace maintenance.
Number One - Change your filter on your furnace!! The frequency of this would depend on whether you have pets, live in a dusty area, etc. The minimum would be once a year. Check your furnace filter monthly and change it if there is any dirt, lint or hair on it. If your furnace does not get air, it cannot work properly. Do not put filters on intake vents. This does not allow enough air for the furnace.
Number Two - Have a professional serviceman check your furnace, clean it and do routine maintenance once a year. We here to help you - your Action Mechanical Plumber.
Call a heating-air conditioning technician if you do not have heat, smell strange odors or smoke from your furnace, or hear strange sounds from your furnace. We here to help you - your Action Mechanical Plumber.