Any guidebook you read will tell you that you should begin your day at Disneyland enjoying the attractions found in Fantasyland. There are several important reasons as to why this advice is given, and it is advice that you should strongly consider following.
Fantasyland is one of the most popular areas at Disneyland because there are no age or size requirements. The only height restriction is a 35 inch requirement for the Matterhorn. As the day progresses, Fantasyland will fill up. Getting there first thing in the morning will help you avoid the long lines that others will encounter later in the afternoon.
None of the attractions in Fantasyland have FastPass. This is another reason as to why you should go there first. FastPass allows you to more or less set an appointment to ride certain rides but none of the attractions in Fantasyland have this option. Cover Fantasyland first, then go get FastPasses for the other attractions that you want to ride.
The crowds and the lines will start growing within a few hours of Disneyland opening each day. Make sure that you arrive before the park opens so that you can be one of the first ones through the gate and head straight to Fantasyland before going anywhere else.
Since all of the guidebooks suggest this, many other early risers will also be headed for Fantasyland. Even so, the lines wont get really long for two or three hours, and by then, you will have already ridden all of the rides there.
From Fantasyland, you should start collecting FastPass tickets for the other attractions that have FastPass throughout the park. It is best to collect these early in the day the longer you wait, the longer it will be before your appointed time comes around, depending on how many FastPasses have been issued for each ride.
While you are waiting for the appointed time for your first FastPass, you should enjoy other attractions, visit the shops, or get a snack. Times between FastPass appointments are great for visiting the restrooms or sitting down to rest with a cool beverage.
Just remember that in order to enjoy the most attractions at Disneyland you should start with Fantasyland, followed by gathering FastPass tickets. Enjoy other attractions between FastPass attractions, but make sure that you dont put yourself on such a tight schedule or such a rigid itinerary that you forget to have fun! Some people simply like to spend some time wandering around the park.