Generally, hotel surcharges on long-distance and local calls are astronomical, so you're better off using your cellphone whenever you can.
The three letters that define much of the world's wireless capabilities are GSM (Global System for Mobile Communications), a big, seamless network that makes for easy cross-border cellphone use. In the U.S., T-Mobile and AT&T Wireless use this quasi-universal system; in Canada, Microcell and some Rogers customers are GSM, and all Europeans and most Australians use GSM. GSM phones function with a removable plastic SIM card, encoded with your phone number and account information. If your cellphone is on a GSM system and you have a world-capable multiband phone such as many Sony Ericsson, Motorola, and Samsung models, you can make and receive calls across civilized areas around much of the globe. Just call your wireless operator and ask for "international roaming" to be activated on your account. Unfortunately, per-minute charges can be high.
For many, renting a phone is a good idea. While you can rent a phone from any number of overseas sites, including kiosks at airports and at car-rental agencies, we suggest renting the phone before you leave home. Alternatively, buying a phone can be economically attractive, as many nations have cheap prepaid phone systems. Once you arrive at your destination, stop by a local cellphone shop and get the cheapest package; you'll probably pay less than $100 for a phone and a starter calling card. Local calls may be as low as 10¢ per minute, and in many countries incoming calls are free.
Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.