Remember that dry chemical extinguishers (the most common consumer type) are harsh on electronics. If you let one loose in your family room to put out that flaming wastebasket, figure on possibly destroying your (previously uninvolved) bigscreen TV, stereo and computer with the powder that will go everywhere. Know the different types, what kind of fires they can be used on, and choose the type most appropriate for the location where you'll have it. Consider whether the extinguisher will put out the type of fire you're likely to encounter with it, and also if it will damage other things while putting out that fire. Unless you go to a specialty store, probably 95% of what you'll find in big-box stores is dry chemical. Which is OK most of the time. But you may want to look at CO2 or H20 extinguishers too if appropriate for your situation (they're more expensive though).