These are tips for general maintenance around the home from the viewpoint of a homeowner (me). I am not a contractor. Comments are always appreciated!
Tip #1: Keep your floor drains full. Floor drains can start smelling if the drain dries up because sewer gases can start getting into the house. Floor drains are common in laundry rooms, utility rooms, and sometimes garages. Guest bathrooms that rarely get used can also have this issue with sinks, tubs, and showers. Here in Colorado, the air is dry, so those drains can dry up pretty quick. I’ll usually pour a little water down my drains once a month or so. You can add a little mineral oil in the drain after adding water, and that’ll help “seal in” the water. Then you won’t have to worry about it nearly as often.