Cell phone tips for jet-setting grads

Bringing your mobile along for your trip abroad this summer? Don't get burned by massive roaming charges. Check out these must-read tips and tricks before you take flight.

We've already regaled you with horror stories of chatty travelers returning home to hair-raising cell phone bills, all thanks to sky-high roaming rates for voice and data calls. (The latest: A man who got stuck with a $62,000 bill after downloading "Wall-E" over his wireless data card in Mexico.)

The main lesson to keep in mind: whenever you're "roaming" out of your home calling area, you should expect to pay handsomely for the privilege of making calls or surfing the mobile Web—anywhere from 50 cents to $5 (or even more) a minute for voice calls, 20-50 cents and up for each text message (sent and received), and anywhere from half a cent to two cents (and up) for each KB of data.

And just to put the data charges in perspective: This very page you're looking at weighs in at about 500KB, or roughly half a megabyte … so if you're roaming internationally, you might get charged anywhere from $2.50 to $10 to browse this (and only this) page on your phone. Ouch.

Ready for the tips? Read on ...

Know the difference between GSM and CDMA
Before you step on that plane, you should know that there are two main types of wireless networks in the world: CDMA and GSM. I won't bore you with the technical details (you can find out more here), but for our purposes, CDMA is more popular in the United States, while GSM is (by far) the dominant network abroad, especially in Europe and Asia.

In the U.S., both Sprint and Verizon Wireless are CDMA carriers, while AT&T and T-Mobile are GSM—so if you're an AT&T subscriber, for example, there's an excellent chance your handset is capable or working overseas (although it might not be enabled for international roaming yet—read on). Options for Sprint and Verizon Wireless phones, however, are much more limited, given that CDMA networks are less prevalent abroad.

GSM phones also have the distinction of coming with "SIM" cards—small rectangular (and removable) pieces of plastic that come embedded with their own phone numbers and serve to identify a handset on a given network. CDMA phones, on the other hand, don't use SIM cards, although some "dual-mode" CDMA/GSM handsets on Verizon and Sprint come with SIM card slots.

Last but least, keep in mind that any cell phone, whether CDMA or GSM, must support a given country's cellular frequency bands in order to work; if you've got a quad-band GSM phone, you're probably good to go, but check with your carrier to see if your particular handset will work in the country you're planning to visit.

Check your carrier's international plans before you go
Want to use your own cell phone while you're traveling? Do yourself a favor and check with your carrier first. In some cases, you must specifically ask your carrier to activate international roaming on your account. Some operators also offer international roaming packages with per-minute discounts for a monthly fee. Finally, check out the international roaming rates on your carrier's Web site before you travel, as calling rates vary wildly depending on the country.

Use a pre-paid SIM card
Don't like your carrier's rates? Well, you could always snap up a pre-paid international SIM card before you go, and just plug it into your unlocked GSM phone (assuming you have one; more on that below). For example, National Geographic offers a pre-paid multi-country SIM card with a UK phone number that works in about 100 countries; you can also buy SIM cards for specific countries and regions (try here and here). The best part: No surprises on your phone bill once you get home. The downside, of course, is that your phone number will change each time you swap in a new SIM card. That said, if you buy your SIM/s before you go, you can always distribute the number(s) to your friends/family in advance.

Unlock your GSM phone, or buy/rent an unlocked handset
If you've got a GSM phone from AT&T or T-Mobile, chances are it's locked to your carrier's network; in other words, your AT&T phone will only work with an AT&T SIM card. So if you want to use a pre-paid SIM with your AT&T/T-Mobile phone, try calling your carrier to see if they'll give you an unlock code. T-Mobile generally will unlock your phone if you've been a subscriber in good standing for 90 days; AT&T may also oblige, although it's an easier process if you're no longer under contract.

Another option, especially for those with CDMA handsets that don't accept SIM cards: Just go ahead and buy a new/used/refurbished unlocked GSM phone (try here and here, for starters). Prepare to cough up several hundred for a feature-packed Nokia phone, although cheap (but stripped-down) handsets are also available for as low as $30 or so. Finally, you can also rent a GSM phone.

Turn data roaming off, and use Wi-Fi instead
No matter how you cut it, data roaming is outrageously expensive, even if you get a data roaming plan from your carrier. AT&T, for example, offers a Data Global Add-Ons for smartphones (including the iPhone), but considering the sky-high prices—$25 a month for a mere 20MB of data, for example—you're not saving much.

Instead, I highly recommend turning off your phone's data roaming capabilities altogether (on the iPhone, for example, tap Settings, General, Network, then switch the Data Roaming setting to "Off") and using Wi-Fi instead. Both open and for-pay public Wi-Fi networks are plentiful in Europe and Asia; just take care when keying in passwords or credit card numbers over an unprotected Wi-Fi network (only do so over SSL-encrypted Web pages).