Imagine going on a trip and staying not in hotels but in other people's homes, for free. That's the premise behind Couchsurfing (www.couchsurfing.org), a free Internet-based "hospitality exchange" service.

Staying overnight in a stranger's home, or letting a stranger stay overnight in your home, might seem like a strange, and risky, thing to do. But it can be a great way to meet people on the road, and meeting people when traveling is the best way to travel. It can also be a great way to meet travelers from all over the world. And the service provides ways to minimize any inherent risks.

Couchsurfing is the largest of similar such services, with others including BeWelcome (www.bewelcome.org) and Hospitality Club (www.hospitalityclub.org). Couchsurfing describes itself as "a community of over 5 million members in 97,000 cities—and every country — around the world."

With Couchsurfing, you can find hosts in two ways. First, you can search for hosts living in or near a city or town you're planning to visit, optionally filtering the list according to such factors as gender, age, suitable for children you may be traveling with, pets allowed, and smoking prohibited. You then send a "CouchRequest" to a suitable person or people, spelling out why you think they would be a good host for you.

Second, you can publish your itinerary, consisting of the cities or towns you plan to travel through, and wait for hosts to invite you. The first way is generally more successful.

Couchsurfing provides various ways to judge the relative riskiness, or lack of it, of its members. All members must write a profile about themselves, which includes a personal description, how you participate in the site, your Couchsurfing experience, your interests, your philosophy, the types of people your enjoy, how you "teach, learn, share," and one amazing thing you've seen or done.

Your profile can optionally include a photo or photos of you, which is recommended. It's easy to upload photos from your computer or other device.

When you stay at someone's home, or when you host someone who stays at your home, you're encouraged to leave a "reference" for that person, which includes a positive, negative, or neutral rating plus whatever verbal description you want. Once you start accumulating references, your acceptance rate increases.

Couchsurfing also lets you become "verified," which is how it makes its money. By paying a $35 "donation," you're listed as a verified member, which the site also suggests builds trust.

Finally, the site makes it possible for you to become "vouched," which is its highest standard of trust. You can do this by being deemed "extremely trustworthy" by three other members who know you personally and who have each become vouched themselves.

When I first started with Courchsurfing, I sent CouchRequests to anybody, including a 19-year-old college undergrad, explaining she looked just like my daughter, that she could regard me as a slightly eccentric but totally cool uncle, and that she should ignore my request if it felt weird in any way. I never heard back from her or other younger people, so I started filtering my requests to those older than 32, 36, or 40, depending on how many hosts were available in any given city or town.

In the beginning I sent requests only to women, feeling they would be more hospitable, but I wasn't getting any acceptances back, so I expanded this to women, men, and couples. I was offered hosting at first with maybe one out of 10 requests, but after I start accumulating positive references from my stays, my success rate improved. Thus far I've been hosted by an equal number of men and women.

The Couchsurfing site recommends that guests bring hosts a gift. But the hosts I stayed with say that guests rarely do. Gifts can include a service offer such as computer help or a cooked meal.

Some hosts have houses, some apartments. Some have a guest bedroom, some literally have a couch you can sleep on or a living room or den floor onto which you can place your inflatable mattress.

The Couchsurfing membership is skewed toward younger people and the more liberal and offbeat. But it also includes folks in their 50s, 60s, and even 70s and those who appear to be more conservative and traditional.

Couchsurfing is a great way to experience a place you're visiting through the eyes of a friendly native and a great way to roll out the welcome mat to a visitor passing through your area.