If you can afford only one power tool, it should be a battery-operated drill-driver. It's a good thing to have around whether you live in an apartment or a house, whether you are a do-it-yourselfer or prefer to have someone do it for you. You'll want a drill-driver that is easy to use right out of the box, will not tax your hand or arm muscles, and can recharge quickly.
Need to know: the power of the battery. Look for drill-drivers with batteries of 12, 14.4 or 18 volts, which are appropriate for typical jobs around the house. But be sure you can handle the tool you buy; the greater the battery power, the heavier a drill-driver tends to be. Lift a few in the store; hold them up for a while. You'll want to be able to use the tool for prolonged periods without muscle strain.
Operating manual: Why does weight make a difference? For example, you're drilling holes so you can hang a window shade. If you can't hold the drill-driver steady, the hole may end up being larger than the screw that holds the hardware, and the shade will be loose because of it. Then you'll have to adjust the location or maybe even drill another hole in the hardware to match a new, better hole in the wood. Avoiding such extra effort is important, whether you'll be using the tool a lot or just occasionally.
Be sure to ask: Does the drill-driver have a keyless chuck? The chuck is the hole in which you put a drill bit that then can be tightened or loosened. In the old days, a drill chuck had three holes; a key was used to loosen or tighten the chuck for drill-bit replacement. Today, what you want is a keyless chuck that allows you to change a drill bit with one hand, freeing the other to hold something else, like a sheet of drywall.
Most jobs require a drill-driver that can hold bits up to three-inches of an inch, but to be on the safe side, a chuck that can handle bits up to a half-inch are better. Such chucks are typically found in tools with higher voltages and are, therefore, more expensive.
Speed limit: Buy a drill-driver with two speed ranges. The lower speed will give you more power to turn screws; the higher speed will provide the power needed for drilling.
Don't do this: Don't buy a cordless drill for a big job that requires more power than a battery can provide. A 12-volt-battery drill won't put holes in a concrete basement floor, for instance; you'll need a drill you can plug into an electrical outlet.
What it will cost: Depending on battery power and other features, a drill-driver can cost $50 to $400. If you are a do-it-yourselfer, from $90 to $200 will probably meet your needs.