With any holiday, there are typically benefits to booking in advance, and that's especially true when it comes to Disney World. Not only will doing so typically guarantee you cheaper flights and a room at your desired resort or hotel, but it will also improve your chances of getting into the latest and most popular dining experiences, including some of the more in-demand like Be Our Guest, Cinderella's Royal Table, Akershus Royal Banquet Hall, and California Grill.
You'll want to book these 180 days in advance or as close to it as possible. If you have any princesses in your party, you may also want to get ahead of securing a seat at the beloved Bibbidi Bobbidi Boutique (located at Magic Kingdom and Disney Springs).
Bonus tip: If, for some reason, you're unable to book a reservation in advance, try doing so in the days leading up to, and even during, your trip. That's when many will make their final selections and surrender tables to avoid cancellation fees. While there are no guarantees, many restaurants also accept walk-ins (opt for off-peak times to increase your chances of getting in and decrease your waiting times).