Keeping drains running
Cooking grease belongs in a container in the trash, not down the sink, since it hardens as it cools. Wipes, paper towels and other items that do not break apart in water stay out of the toilet, and a strainer in the shower catches hair before it reaches the trap.
When the clog is past your property line
In San Diego the property owner looks after the sewer lateral from the house all the way to the city main, even where that connection sits in the street, on an easement or in a canyon, so keeping it clear along its full length falls to the owner.
Clogs that come back after clearing can mean a damaged lateral for sewer repair, and a worn stopper or trap belongs under fixture repair. The homepage has the full list.