Almost everyone has a few smoke detectors and a fire extinguisher somewhere in their home. If you don’t, you definitely should, and are required to by law in California. Unfortunately, that’s as much care as many people take in their fire safety. That may not be enough.
Smoke detectors should be spaced around your home so that they can be heard regardless of where you are. California requires smoke detectors in certain areas of the home. This includes every bedroom, every hallway that leads to a bedroom, and at least one per floor in a living area. Check to make sure that you are conforming to code, and that your smoke detectors have working batteries. If your home is large, you may also want to consider additional smoke detectors above the minimum requirements to cover more area.
Homes are only required by law to have one fire extinguisher. However, this is the bare minimum and not ideal. You want to have easy access to a fire extinguisher regardless of where you are. The suggested number is one per floor. If you live in a multi-family building, every unit should have easy access to a fire extinguisher. This doesn’t necessarily need to be inside the unit, if there are hallways with access to multiple units. But having just one for the entire building isn’t a good idea, even if there are only a few units.