It's an old story, but here we go again: One caller into a CNN TV show sounded like a man on his very last legs as he explained how a trip to Mexico turned abruptly expensive. No, "Alberto" wasn't kidnapped and held for ransom by a drug cartel. He was the victim of his cell phone carrier, who slapped him with a $62,000 bill after he downloaded a copy ofWall-E to his laptop via his cellular data card.

Alberto's not alone: Tales of multi-thousand-dollar cell phone bills are legion (I've written about several of them here), but looking through the cases you'll see a few common themes over and over again. Want to avoid getting slapped with a bill that's higher than the price of a new car? Here's some advice that every cell phone customer should keep in mind.

> International roaming is often the enemy in cases like this. Neither standard voice nor data plans cover calls when you're out of the country, and yes that includes Mexico and Canada. I've even heard of one case where a caller got a mega-bill while standing on a boat docked in Miami but which was deemed "international" until he could prove he was still in U.S. territory. International roaming rates are exorbitant and are billed by the minute (usually over a dollar/minute) or the kilobyte, so your best bet when leaving the country is to leave your cell phone at home if you can -- or call your phone carrier to ensure that international roaming is disabled so you won't be billed for accidental calls or automatic data pings like the iPhone performs.

> If you need connectivity overseas, make sure you understand the rate you're paying. $1.29 a minute is easily understandable but $0.0195 per KB doesn't mean much to many data users. That tiny number adds up quickly. Case in point: Downloading a single, simple web page like this one will run you about eight dollars. Now imagine downloading a one-gigabyte movie and you'll understand how these five-figure bills happen. Leave your data card behind!

> One strategy many travelers undertake is to buy a prepaid SIM card they can use overseas or get a cheap phone if they don't already have one that's compatible. In Europe, pay-as-you-go plans can be had that offer calls for about 30 cents a minute. If you don't have a GSM phone, you can get one at any cell phone shop for $30 or less. None of these plans require long-term contracts. You just pay for the minutes you use.

> The other major issue with big bills is going over your plan's data cap or allotment of minutes. Data's the biggie: Most wireless data plans top out at 5GB, after which you pay by the KB. The rates aren't as egregious as they are for international use, but downloading that 1GB movie after you've exhausted your 5GB of data will still run you an extra $500. Carriers allow you to check your data usage online, so make liberal use of that feature if you think you might be getting close to the cap.