8. Read this story on your mobile phone without a data plan

If you're reading this page on your mobile phone and you have no idea what a data plan is, close your browser now. Worse, if you are reading this page on your mobile phone overseas, turn it off now and check your bank account for sufficient funds.

Data charges can amount to quite a hefty sum, and this is especially true for mobile phone uses with no data plan.
Surfing the Internet, receiving and sending email or chatting on instant messaging are just some of the things you can do with smartphones that require a data transfer. Because your local telco doesn't belong to Santa Claus, data transfer isn't free.

If you're overseas, data charges are even higher. Loading a simple, regular webpage like this can run up to about (gasp!) $8.

The bottom line: If your phone has Wi-Fi, make sure that function is turn on instead of the 3G feature when surfing the web. Want to use more broadband services while on the go? Get a data plan. For those going overseas, check with your destination country's local telco to see if there are any prepaid card plans and dongles for sale or rent. They won't come cheap, but at least you don't have to pay hundreds or thousands of dollars in phone bills.

Read more: Don't end up with a $20,000 phone bill