Although heist movies star clever criminals who defeat even the most sophisticated security measures, few of us need systems strong enough to thwart Ocean’s crew. It doesn’t take a lot of smarts or knowhow to be a burglar: Most get in simply by opening unlocked doors or windows—or quickly breaching poorly secured ones.

The good news is that simple tasks will greatly improve the security of most residences. First step: Install good locks on doors and windows and get in the habit of using them. Consult our ratings of locksmiths if you need help with that.

Also know that only about one in 50 U.S. homes get broken into each year. Over time, however, the odds turn against you, so it makes sense to shore up your defenses.

Before springing for an expensive alarm system, take some basic steps to greatly improve your security for little or no cost.

1. Secure the perimeter.

It doesn’t take a genius to be a thief. Professionals who can pick locks and circumvent alarm systems commit a very small portion of burglaries. Most criminals enter homes by opening unlocked doors or windows; lifting sliding glass doors off their tracks; prying open weakly defended doors, windows, and garages; or using unauthorized keys. Intruders prefer visual obscurity, silence, easy entry, and quick exits. Your primary objective when planning home security, then, is to beef up your locks and latches, and maintain good security habits. We details ways to improve your home's physical barriers in the next article.

2. Get a home security audit.

Most police departments provide free advice and will send someone to evaluate your home for weaknesses.

3. Get insurance.

Maintain adequate homeowners or renters insurance to cover property losses due to burglaries. Our evaluations of homeowners insurance companies and advice on getting the best deal will help you decide what to buy and who to buy it from. Certain items (jewelry, cash, electronics and computers, and guns) usually are covered at low limits; consider buying extra coverage for them.

4. Buy replacement cost protection.

Without a replacement cost provision, homeowners insurance policies cover only the “market value” of personal property, not “replacement value.” Market value is defined as the replacement cost minus depreciation. Insurance companies typically offer the option of covering the full replacement cost (with no deduction for depreciation) for 10–20 percent more than the standard policy. If burglars clean out your home, coverage for full replacement cost could save you thousands of dollars.

5. Take an inventory.

Having a list of your belongings will help you get compensated if you suffer a major loss from burglary or fire. Prepare a list of expensive possessions, including purchase dates and prices, then move through your home and record a video of the rest. Update your inventory every couple of years.

6. Get appraisals.

If you own antiques, expensive jewelry, original paintings, or other items of substantial value, get written appraisals for them—but make sure your appraiser is acceptable to your insurance company. Tell the appraiser that you want the evaluation for insurance purposes. Many are dealers, and if they think you want to sell the items, they might lowball the estimate of their value.

7. Participate in Operation Identification.

This involves engraving an ID number on your valuables and putting a decal in your window. This will deter some burglars if clearly marked items are harder to sell. Although only about 10 percent of burglarized homes recover any stolen stuff, positive identification improves your chances.

Metal engravers cost from $8 to $25. Some police departments lend them out; call yours to see if one is available.

There are also various ways to “fingerprint” fine art, jewelry, and other items without damaging them. Ask an appraiser or jeweler for help.

8. Keep valuables out of sight.

Place articles of ostensible value out of the view of anyone at your front door or easy-to-see-into windows. Stash cash and expensive jewelry in unlikely places—for example, in a large envelope or among many paper files. Select containers no one will accidentally discard.

9. Lock up guns.

Burglaries are major sources of guns for criminals, although estimates of the percentage of crimes involving stolen guns vary widely. Each year more than 100,000 guns are reported stolen—but no one knows how many more gun thefts are unreported (some studies estimate over 60 percent). Trigger locks can prevent accidental shootings but not thefts. If you have guns, store them in locked gun boxes or on gun racks that cannot be easily removed. Another option is to use a Simplex lock, which is a small gun safe opened by pressing five buttons in a specific order, a process that can be done quickly even in the dark. Steel gun boxes with Simplex locks usually cost $150 and up.

10. Install a safe.

Small fire-resistant models with about one cubic foot of storage cost $100 to $200; many models can be bolted to the floor. Safecrackers can open them, but other burglars usually can’t. Highly secure—but much more expensive—safes are also available.

11. Rent a safe deposit box.

A box may be inconvenient, but it provides a level of security against theft and fire that cannot be duplicated at home for less than several thousand dollars.

12. Make them think someone is home.

Most burglars strike when no one is home, so make sure your house appears occupied. Leave music or a TV on, and keep your garage door closed. Plug a light or two into timers to turn them on at dusk and off at bedtime.

13. When you’re on vacation, keep up appearances.

So that mail and packages don’t pile up, place a mail hold at the post office or ask a friend or neighbor to collect them. Arrange for your lawn to be mowed or your sidewalk shoveled, if needed. Leave a car parked in the driveway.

14. Consider getting a lock for your bedroom door.

Since you spend more than half of your time at home in your bedroom, you may also want to install a solid-core door with a heavy lock on it. If you don’t have kids, you can then sleep with your bedroom door locked. If you have kids, sleeping behind a solid locked door probably sounds like a fantastic plan for more rest and privacy, but it’s bad in terms of safety. On the other hand, if you have a bedroom door that locks you can retrieve your kids and lock out home invaders.

15. Keep landscaping in check.

Doors and windows hidden by garages, bushes, fences, and trees are attractive targets for intruders who prefer to invade unseen. If possible, keep areas around your doors and windows visible from the street—to your neighbors and from within your house.

If it’s impractical or unattractive to hack back your home’s jungle, consider planting thorny varieties close to the house so prowlers won’t hide behind them. Garden centers and landscapers can advise you on what to plant and give you help planting it.

Large trees may provide access to upstairs windows or, more often, to a porch roof near a window. Consider pruning them.

16. Fence it in?

A high fence is a double-edged sword. It can make it more difficult for an intruder to get in and out, but it also can hide a burglar. If you have a gate, keep it locked so an intruder knows the fence would slow his escape.

17. Secure tools.

Crowbars, hand tools, or yard tools lying about outside the house or in open garages invite trouble. Lock up any implements that could be used for prying or bashing. Also secure ladders.

18. Light it up.

Most nighttime prowlers flee the moment indoor lights go on, but bolder ones might hide until you go back to sleep. An outside light will chase away all but the nerviest.

Use outdoor lights to illuminate the entire exterior of your house or vulnerable areas. They can be set for all-night operation or to power on when triggered by motion.

For the greatest security, external lights should have break-proof lenses, strong mountings, hidden wiring, and tamper alarms. Find security lights online or at some hardware stores, electrical equipment suppliers, and locksmith shops.

Professional installation of a whole-house security light system costs $1,000 to $3,000—and increases your electric bill. A do-it-yourself installation at one point of vulnerability may cost less than $200. Unsecured outdoor lights with outdoor sockets (which usually take reflector lamps) cost much less, but a careful intruder can remove the bulbs.

Place the switch for any outdoor light or lighting system intended to provide security in a convenient location away from the light. You probably won’t want to run downstairs to turn on a light when a prowler is breaking through a nearby door.

19. Keep track of keys.

Intruders also invade homes with keys “hidden” under your doormat, kept by a contractor, or copied from a key lent to a plumber or parking-lot attendant, or…you get the idea.

When you move into a house or apartment, consider having all the lock cylinders replaced or re-keyed. If you often must give a house key to anyone you don’t fully trust, consider installing restricted key cylinders, which take keys made with special cutting equipment and require your authorization to make duplicates.

20. Work with your neighbors.

Neighborhood watch groups can cover a single block of 10 or 12 houses or dozens of blocks with 1,000 houses. Most get training from police officers on security measures, ways to spot suspicious activity, and how to keep in contact with the police. Some neighborhoods even form citizen patrols of volunteers who look for suspicious activity that they report to the police.

21. Get a watchdog…

Dogs can offer added security in multiple ways. First and least is the family pet with no particular training in sounding an alert. Performance varies tremendously, depending on its breed and genealogy, gender, individual idiosyncrasies, and life experiences. Dobermans and German shepherds get a lot of respect from intruders. A concern, of course, is that your untrained dog will attack innocent strangers, your neighbors, or their children.

The second level is to train your dog to bark at—but not attack—strangers. This usually requires hiring a professional trainer.

The third level is a personal protection dog professionally trained to attack on command or when he or she thinks a family member is being assaulted. Unfortunately, even most watchdogs have trouble distinguishing between a friendly slap on the back and a real assault. Many are unreliable except when handled by their family.

22. …Or bluff that your dog is a menace.

You can post a “Beware of Dog” sign at the front entrance of your house—even if you have no dog or the dog you do have is afraid of strangers, loud noises, all creatures large and small, the wind, and pretty much any moving object.