If you typically end up with gouged drywall, rounded screws, or scratched tile when you use a cordless drill, don't give up on doing the job yourself. The following tips will help you avoid these and other mishaps and will turn you into a drilling maven. Before you start any project, remember to wear safety goggles to protect your eyes. And if your drill produces noise levels above 85 decibels, wear hearing protection. (See our Ratings, available to subscribers, for a list of tested models that scored Fair or Poor in our noise tests.)

• Hold it straight. Prevent crooked holes or fasteners by holding the drill perpendicular to the work, not at an angle.
• Use both hands. For better leverage, especially when using a tool in hammer mode, attach the second handle to the drill. (Found on a growing number of models, hammer mode rapidly pulses the chuck and bit forward and back to punch through cement and other masonry. Note: Always use a masonry bit when working on these materials.)
• Use the right speed. Most drills have two speed ranges. Use the low range for driving screws, nuts, and bolts, and the high range for drilling in any material.
• Check the clutch settings. Many drills have 16 or more settings that let you limit torque to prevent stripped screws and marred finishes. Use a lower setting for drilling or driving into softer material, a higher setting for harder surfaces.
• Drill a small hole first. Drilling a pilot hole, especially when working with metal and hardwood, makes it easier when you switch to the bigger bit you'll need for larger holes. For example, if you're drilling a 1/4-inch hole, begin with a 1/8-inch hole in that spot. When drilling in tile, use a glass/tile bit. It's shaped like a spear, and its sharp pointed tip prevents it from skipping on the tile. You do not need to drill a pilot hole when using one of these bits.
• Don't cheap out. When buying drill or driver bits, look for ones made of hardened steel. They cost more, but the hardened steel wears longer.
• Store batteries at room temperature. Extremely cold temperatures can prevent nickel-metal hydride batteries from delivering their full power.

Tips specific to impact drivers

These tools look and act much like cordless drill/drivers, but there is a difference: An impact driver gives up some drilling speed for added torque (twisting power) to loosen stuck screws and smoothly drive thick bolts through hardwood. This power doesn't come quietly. All of the impact drivers we tested are loud enough--more than 85 decibels at the ear--for us to recommend hearing protection.

• Use the right shaft. When drilling with an impact driver, use bits with a hexagonal shaft. Because impact drivers are best at driving, drilling work will go more slowly than with a good drill/driver.
• Don't overtighten. Unlike drill/drivers, impact drivers lack multiple speeds and a torque-limiting clutch. For automotive lug nuts and other fasteners with specified torque settings, tighten the fastener only partway with the impact driver. Finish using a torque wrench (about $50) adjusted to the proper setting, typically in foot-pounds.

FOR MORE INFORMATION Our new report on cordless drills will fill you in on the latest technological advancements for these tools, which are stronger and run longer than ever. See our Ratings (available to subscribers) to see how the drills performed in our tests.