Important Features you should know before buying a cordless drill include:

A "Smart" Charger. Recharges a drill's battery in about an hour or less. Compare that to a conventional charger that needs three to five hours or more to charge.

Smart chargers also extend battery life by adjusting the charge as needed.

Most smart chargers switch into a maintenance or "trickle-charge" mode as the battery approaches full charge. One drill has a dual charger that charges two batteries at once.

Most cordless drills 12 volts and more have two speed ranges: low for driving screws, high for drilling.

A Low speed provides more torque, or turning power, than the high-speed setting, which is useful for drilling holes.

Most models also have a variable speed trigger, which can make starting a hole easier, and an adjustable clutch, which lowers maximum torque to avoid driving a screw too far into softwood or wallboard, or mangling its head.

Most drills have a 3/8-inch chuck, but some higher-voltage models have a 1/2-inch chuck, which can accommodate drill bits up to 1/2 inch. (Large diameter bits with a reduced shank will fit in smaller chucks.) 

Many new models are also reversible, letting you more easily remove a screw or back a drill bit out of a hole.

Still other features make some drills easier to use than others.

Some models have a second handle that attaches onto the side of the drill so you can use two hands for better control when driving large screws.

All but the least expensive drills come with two batteries, letting you use one while the other charges.

Most cordless drills run on nickel-cadmium (NiCad) batteries, which can be recharged hundreds of times.

Once the battery is depleted NiCads must be recycled, since cadmium is toxic and can leach out of landfills to contaminate groundwater if disposed of improperly. Incineration can release the substance into the air and pose an even greater hazard.

A few models run on nickel-metal-hydride (NiMH) batteries, which don't contain cadmium and are friendlier to the environment.