Reading travel guides before your trip is a great way to prepare. You can learn general advice for travelling, plan out weekend trips, and find activities that match your interests. UNC-Chapel Hill Libraries own a number of basic guidebooks to Mexico, but you also might consider buying an up-to-date copy of your favorite guidebook to take with you.
Let's Go, the Rough Guides, Lonely Planet, and Fodor's are all good places to start your online search for travel information. Click the images on this page to get to their information about Mexico.
Also, it is always helpful to read the State Department's Consular Information Sheet on Mexico before you travel there.