Cleaning a gas fired furnace essentially comes down to cleaning the burners and the pilot light. While you should ideally have your gas furnace checked by a repair person once a year, you can perform simple maintenance periodically. While the specifics of gas fire furnaces vary from one model to another, these cleaning jobs follow the same basic methodology.
Shut off the main gas valve and turn off the power at your home's main's service panel. Most utility companies also install a unit disconnect switch that should be turned off before cleaning begins.
Loosen the spuds with a ratchet wrench and remove spud. Inspect the spuds for signs of dirt or wear and tear. Use the soft-bristled brush to clean the spuds. Use a toothpick or a piece of wire to insert into the spud opening to clear the inside. Make sure you don't chip the opening. Replace the spud inside the furnace and gently tighten it onto the manifold.