Replacing the battery in a smoke detector

Today is the beginning of Daylight Saving Time in (most of) the United States. While you’re going around your house setting all the clocks forward an hour, it’s a good idea to check the batteries in devices like smoke detectors, carbon monoxide detectors, and radon detectors. And, you know, any other devices you depend on to keep you safe or enable you to earn a living but which run on batteries that might inconveniently die at the worst possible moment.