Prepare for it to be absolutely mobbed. It can often take up to 45-60 minutes or more (usually more) just to get from your car, through security, and through the main gate. Add that in to your schedule.
Research as much as you can, especially if there are any particular places to eat. If you can make a reservation, do so as soon as possible.
Get as much done in the morning hours as you can. Once 10:30 or 11am arrives, so do the crowds... and they never really leave after that.
Disneyland is a great park, but it wasn't built for the current crowd levels it's experiencing. Many walkways are very narrow, and are often jam packed with people, strollers, and wagons. Bring a lot of patience.
Get your Maxpass for major attractions as early as possible... they can "sell out".
Aside from that, there's a lot of websites out there to give you tips.