If you are staying at a Disney Resort, you can make up to 10 days worth of ADRs when you reach 180 days from check-in. You can book on-line at
disneyworld.com/dining beginning at 6 AM Eastern. You can call Disney Dining at 407-WDW-DINE beginning at 7 AM Eastern. You can call MS beginning at 9 AM Eastern. If you call either Disney Dining or MS, they will book them (subject to availability) while you are on the phone with them. NOTE: The on-line system may or may not allow you to book past 180 days.