There are many wonderful travel guides. My personal favorites are the DK Eyewitness Guides. Full of beautiful images, they paint a picture of why you might want to see and experience the many beautiful parts of the world. I also find Lonely Planet guides particularly useful. Although they are not as graphical, they are full of detailed information that you really ought to know when going to a new place. Travel guides are becoming increasingly popular in the form of mobile apps for smart phones and iPods lightening the loads in our backpacks. Travel magazines like my favorite National Geographic Travel, are another great source of ideas and snippets of useful information.
Despite all of the wonderful resources available, the best travel guide is a local. Well-informed locals who wants to help travelers to experience the places they call home are the best sources of travel knowledge. Not every local desires to help or knows the information that travelers need. The trick is finding and learning from those who do.