Replace a door lock. If you buy a house someone else previously lived in, you might want to replace the exterior locks. On the inside of the door, remove the two long bolts holding the front and back of the lock together; remove the front and back of the lock. On the edge of the door, remove screws holding the latch in place and pull the latch out. To replace, add new hardware in reverse order.

Before buying new hardware, check the "backset," or the distance from the edge of the door to the center of the hole for the deadbolt or doorknob. Replacement hardware will need to match; some locksets are adjustable and accommodate the two standard backsets.

Change furnace and air-conditioner filters. Be sure you know where all the filters are - on air returns or at the air handler. Make a note of filter sizes and keep the information handy.

Also, learn how to clear the pipe that carries condensation from the air handler during the cooling season. The pipes can get clogged with mold and algae and the water will back up. If your air handler is in the attic or a utility room, it should have two drains: one from the unit, and the other from the safety pan under the unit.

Learn the location of the main water cutoff. It's probably in a utility room or closet, but could be at a water tank or near the meter. Familiarize yourself with other cutoffs, too: the dishwasher and icemaker, for instance.

Learn, too, how to turn off the gas in an emergency: Gas valves, indoors or at the meter, are open when parallel to the line and closed when perpendicular.

Find a stud in a wall. You'll want to locate studs any time you're hanging a heavy object, or installing molding or cabinets. Most homeowners know the tap-tap-tap routine; you'll get a hollow sound between studs, a solid thunk on the stud. The centers of the studs are 16 inches apart - so if you find one you can usually locate the others.

A tip: Look for the heads of finishing nails near the top edge of the baseboard. Those nails will be in studs.

Master hollow-wall anchors. Use these for spaces between studs, to mount towel bars, drapery rods and the like. Match the anchor to the weight of what you're mounting. From weakest to strongest, anchors include: plastic expansion anchors, threaded drywall anchors (Zip-It), winged plastic anchors, molly bolts (sleeve-type anchors) and toggle bolts.

When installing anchors, you can make small holes in drywall with an awl or sharp nail, but you should use a drill for larger holes. You'll be more accurate if you make small starter holes even for anchors that screw in.

Hang a ceiling fan. This involves skills you'll also use to replace light fixtures and receptacles. The first step, any time you're dealing with electricity: Turn off the power at the breaker box.

You must make sure a ceiling fan is anchored properly. If it's not, it can fall. If you can move the electrical box with one finger, it won't support the fan. Anchor directly to the ceiling joist.

Assemble the fan, minus blades. Then attach the fan's ceiling bracket. Hang the fan in the bracket. Connect wires - black to black and white to white - according to the directions. Attach blades. Fans work best if the blades are at least 10 inches from the ceiling; fans should be no lower than seven feet from the floor.

Make sure wires are securely fastened and avoid jamming them into crowded boxes. If you try to force wires, you could pull them apart and create a dangerous short.

Drive drywall screws with a variable-speed drill. You'll repair drywall nail pops that way, of course. Pull the nail, drive a screw into the stud or joist a few inches away from the nail hole. The screw head should "dimple" the surface, with the screw head just below the face of the drywall. Cover the screw head and nail hole with spackling, let dry and sand.

Driving screws with a drill is like putting in golf: It's all feel. Practice on a scrap of 2-by-4. Also, buy extra No. 2 Phillips screw bits. You'll tear them up, especially when working on decks, which require the same skills.

Master a caulking gun. A gun's trigger gives you more control. But there are some tricks. Cut the tip of the tube at an angle, but with a smaller hole than you think you might need; you can always trim the tip again if the hole needs to be larger. Break the inner seal.

Quit squeezing before you get to the end of the area you're caulking. The caulk will continue to come out. When you reach the end, lift the gun from the surface and immediately remove the tension on the push rod.

Seal stains before painting. You can't paint over crayon, ballpoint pen, grease splatters or water marks without the stains coming through. You must seal them first.

There are lots of good sealers and primers these days, but one old standby is pigmented shellac. A familiar brand is B-I-N from Zinsser, and the company's Web site (www.zinsser.com) is a good place to learn about the wide array of specialty primers.

Remember that you can tint primers to make them easier to cover with the finish paint. Some primers, including pigmented shellac, seal in odors, too, such as cigarette smoke and litter-box smells.

Replace the flapper ball in a toilet. Every homeowner deals with a toilet that leaks water from the tank to the bowl (and mysteriously flushes in the middle of the night). The problem is usually a bad flapper ball, the valve that opens when you press the handle to flush. The cure is easy: Buy a replacement, read the directions on the back of the package, install it.

Pay attention to chain length. Too short or too long can interfere with proper operation. Also, clean the opening at the bottom of the tank before installing the new flapper ball. Grit and minerals can build up and keep the ball from seating properly.