Decide when you want to take your vacation and how many days you plan on staying there. The spring and fall are pleasant, the summer is hot and the most popular tourist season, and the winter can be cold, maybe even offering snow and is the least busy time of the year. If your vacation is going to be longer than three days, you can include a trip to Las Vegas, the Hoover Dam, Phoenix or a number of other destinations that are within half a day's drive from the Grand Canyon.
Choose which part of the Grand Canyon you will visit. The South Rim is the most popular destination and is open year round. There are more amenities available in the South Rim, which tends to be better for first-time visitors, large groups and families. The North Rim is open from mid-May to mid-October and offers a more low-key and intimate experience. The Grand Canyon West and Hualapai Indian Reservation are better choices to avoid high altitudes, to visit the bottom of the canyon, or for shorter visits.
Figure out what kind of transportation you'd like to use. The closest major airports are in Phoenix, Arizona and Las Vegas, Nevada. You can drive, fly, or take a bus or train to the Grand Canyon. If you are driving, be sure to fill up your gas tank every chance you get and take plenty of water. It is in a remote desert, after all.
Make reservations for everything you can as far in advance as possible, including transportation, lodging, tours and restaurants. You can order videos, trail guides, maps and other packages that will help you plan your trip as well. (see References)
Confirm all of your reservations one week before you are set to leave. Keep a list of each reservation number, time and date and appropriate contact information with you, just in case you need that information.