Because most burglars enter homes by opening unlocked doors or windows, before shelling out big bucks for an alarm system or other gadgets, take some basic measures to improve your home's security. Many of the most effective security strategies cost nothing or very little.

For detailed advice on home security, visit Checkbook.org/StarTribune/HomeSecurity.

• Secure the perimeter. Make your doors and windows as difficult to penetrate as possible. Although intruders prefer unlocked doors and windows, many can quickly and almost silently pry open locked ones. Some break a pane of glass so they can reach in and unlock the window or door. Only a few really determined burglars break out enough glass to walk or crawl through.

• Lose lousy locks. Key-in-the knob locks are inadequate. Install good deadbolt locks on all your exterior doors.

• Secure sliding glass doors. The locks on sliding glass doors are notoriously flimsy. Numerous how-to videos on the Web can show you how to make yours more secure, or you can pay a locksmith to install reinforcements.

• Replace weak doors. Solid-wood doors are much sturdier than hollow ones. Many homeowners in high-crime neighborhoods install metal bar doors.

• Secure your windows. Depending on the type of window, you can take various steps to make it more resistant to a prying attack. Double-hung windows, for example, can be secured by screwing together the two frames. For the highest level of protection, the window should have unbreakable glazing or steel bars across it.

• Keep valuables out of sight. Place articles of ostensible value out of the view of anyone at your front door or anyone looking through your front windows from the street. Stash cash and expensive jewelry in unlikely places — for example, in a large envelope or among many paper files.

• Rent a safe-deposit box. A box may be inconvenient, but it provides a level of security that cannot be duplicated at home.

• Keep your landscaping in check. Doors and windows hidden by garages, bushes, fences, and trees are attractive targets for intruders who prefer to invade unseen.

• Light it up. Many burglars will flee if they activate an outdoor light connected to a motion detector.

• Keep track of your keys.

• Get a dog. Many burglars avoid homes with noisy, furry, family members.

• Get to know your neighbors. At the very least, share information on your not-at-home schedules and vacation plans.

• Keep up appearances. If you go on vacation, work with neighbors or friends to prevent mail and packages from piling up and to keep your lawn mowed and your snow shoveled.

• Lock up guns. Burglaries are major sources of guns for criminals.

For millions of households, an alarm system is one component of a home-security plan, and there is much evidence that these systems do make a difference in deterring burglaries. But living with an alarm system is at best an inconvenience, at worst enough of a hassle that many homeowners don't use theirs regularly. Homeowners continually turn off their systems to prevent false alarms.

Basic alarm protection should cover all exterior doors and any windows easily reached by intruders. Professional installation meeting these criteria usually costs $1,000 to $2,000. Some companies offer steep discounts to customers who sign long-term monitoring contracts. With these companies, you can get a basic system for less than $500 if you sign a three-year monitoring deal.

Moderately heavy alarm protection covers other points of potential entry, plus will use motion detectors, pressure pads, and sensors on cabinets and bureaus to detect intrusions past the perimeter. Such systems usually cost from $1,500 to more than $3,000.

Even if you purchase a home-security system with all the bells and whistles, it might not do you any good if it's designed poorly or installed sloppily. The ratings and reviews submitted to us at Consumers' Checkbook, plus reports from our undercover shoppers, indicate that the expertise of home-security representatives varies greatly.

On the other hand, some companies' reps are true experts. Many salespersons have performed installation work in the past, and some install the alarm systems they plan themselves.

You will also find huge company-to-company price differences. When Checkbook's undercover shoppers collected proposals from companies for specific alarm systems and three years of monitoring services for four different homes, they were quoted prices ranging from $1,434 to $3,828 for one of the homes and $4,270 to $8,314 for another.

Twin Cities Consumers' Checkbook magazine and Checkbook.org is a nonprofit organization with a mission to help consumers get the best service and lowest prices. We are supported by consumers and take no money from the service providers we evaluate. You can access all of Checkbook's ratings of home security companies and locksmiths free of charge until April 5 at Checkbook.org/StarTribune/HomeSecurity.