This one is just common sense. If you're traveling and roaming on your phone, you're bound to rack up a considerable charge. After all, if you're a frequent traveler, the convenience of using your mobile network can make it easy to forget the extortionate internet bills you'll accrue. The easy way around this is to check the WiFi situation at every hotel you stay at. Then, log in and make the most of the free internet when you've got the code.
If you're planning on visiting multiple places, it's worth planning your schedule while you have this connection. Likewise, download movies and music in advance so that you don't have to while you're roaming.