It's not just a catch phrase, smoke detectors really do save lives.
You should have a working smoke detector on each level of your residence. It is also inportant to have smoke detectors outside of sleeping areas.
Remeber to change the batteries in your smoke detector (and Carbon Monoxide detertors) every 6 months. A good time to change the batteries is when you need to change the clocks for daylight savings time. This occurs every 6 months (April and October) and is an easy way to remeber when it's time to change your batteries.