We've watched readers on our Message Boards discuss the best ways to make calls while they're out of the country, and we wanted to pitch in with some help.

First of all, if you're going to Canada or Mexico, call your cell phone carrier and tell them. Most American phones work in Canada and at least parts of Mexico for relatively reasonable per-minute rates.

For the rest of the world, you have three options: international roaming with your US carrier, renting a foreign phone, or buying a SIM card from a company like Telestial (www.telestial.com). Depending on the kind of traveler you are, each of the three might be the cheapest or best choice.

For Just a Bit of Calling, Roam

If you only plan to use less than an hour's worth of phone time during your trip, or you're a business traveler who absolutely needs to be reached at your US number, all of the major US wireless carriers will let you take your number abroad. All these plans are expensive: at least $1/minute whether you're making or receiving calls, and often much more.

If you're a Cingular, AT&T or T-Mobile subscriber with a "tri-band" or "quad-band" phone (if you don't know, ask your carrier), you can just ask your carrier to turn on international roaming and pow, the phone will work in most of the world (except, notably, Japan and Korea.) The same goes if you're a Verizon subscriber with a Samsung A790 phone.

Verizon subscribers with other phones going to Bermuda, China, the Dominican Republic, Israel, New Zealand, South Korea, Taiwan or Venezuela can ask for "international roaming" and use their own phones abroad, most of the time (check with Verizon to make sure your phone can do it.) Ditto for Sprint customers going to China, most of the Caribbean, Argentina, Bolivia, Chile, Guatemala, Honduras, Paraguay, Peru, Uruguay or New Zealand.

Verizon, Sprint and Nextel subscribers going to other locations who want to keep their numbers can rent international phones from their provider for a weekly fee plus a per-minute charge. It isn't cheap, but it's often the best solution for businesses.

Looking for real, solid prices? Click the carrier below to go to information pages for calling internationally:

If You Have The Right Phone, SIM it

If you want to make or receive more calls and you have a phone that would work abroad (one of those AT&T/Cingular/T-Mobile models), call up your carrier and ask to "unlock" the phone because you're going abroad. Usually, they'll give you a code that will then let you temporarily use another company's service when you're overseas. Then get a local, prepaid SIM card for the destination you're traveling to. (A SIM card is a tiny chip that holds your subscription information.)

Using a local SIM card means incoming calls are usually free within the SIM card's primary country. Outgoing call rates are much lower than if you're roaming with a US phone: usually 25-60 cents for in-country calls and a bit under a dollar for international calls, though sometimes they're even cheaper. (In India, for instance, in-country calls on a local SIM are around 10¢ per minute and calls to the US are 37¢ per minute. Roaming calls using an American AT&T handset, on the other hand, are $2.29/minute -- and that's a good rate for roaming.)

True cheapskate travelers can usually just traipse into a phone store in their destination country and buy a SIM card. But language barriers can make that a chore, and some countries make it even more difficult: in France, Italy, Russia and Switzerland, for instance, foreigners can't buy SIMs. That's where Telestial (www.telestial.com) comes in. Telestial is a US-based company that resells foreign SIM cards to Americans who don't want to brave phone stores in Rome where everyone only speaks Italian.

Telestial charges a markup for its SIM cards -- typically, a $39 European SIM card becomes $59 on Telestial's site -- but Telestial president Ken Grunski agreed to cut Frommer's readers a deal. Punch in coupon code frommers01 when you're shopping on Telestial.com, and pow, you'll get 15% off any purchase.

Grunski also points out that by shopping through Telestial, you save time and hassle. Buying a SIM card where you don't speak the language can be a real pain. I've done it. It involves a lot of pointing and hooting, and usually an hour in the cell phone store figuring out what tariff you need. Telestial holds your hand every step of the way, giving you support on setting up your foreign card and letting you find out your new foreign number before you leave home, so you can give it to your friends.

If you're heading to one specific country, just go buy a Telestial SIM card for that country. You'll get the lowest possible per-minute rates. You can also take those single-country cards to neighboring nations, but the rates go up. (All the rates are on Telestial's site -- there are far too many to list here.)

If you intend to roam Europe, get a Riiing card instead. Riiing costs $39; incoming calls throughout Europe are free, and outgoing calls generally cost 60¢-85¢ per minute, according to Grunski. That's more expensive than a single-country card, but less expensive than taking a single-country card out of its homeland.

No International Phone? Buy Or Rent

Infrequent international travelers without a world-ready phone can consider renting a phone with service from a company like Travelcell or Roadpost, both of which have deals for Frommer's readers. (See our column at www.frommers.com/articles/2528.html.) If you're traveling to the right country, you might even get free incoming calls; outgoing calls can cost a whopping amount, though, well over $1/minute. That can make renting very expensive if you intend to make more than a few outgoing calls.

So, like me, you just may find it cheaper to just buy a world handset and then pick up international SIMs wherever you go, to get those low local SIM rates. I have a Sony Ericsson phone that I just throw into my bag whenever I leave the country; I've had it for three years now. Telestial sells the pretty basic Motorola 3788 for $99 (with the Frommer's discount, that's $84.15). It's old and isn't very pretty, but it makes phone calls and sends text messages. And that's all you need, right?

Talk about cell phone options on our Message Boards today.