Disneyland and Disney World are a bit different on their Fastness systems. For Disneyland it’s the original system where you secure passes early and often and have more leeway.
For WDW they use Fastpass+ now, so you basically need to mark your calendar for when your window opens to book fast passes and grab them online long before you’re at the park. For dining reservations at WDW you’re best off calling the day your window opens too, since there are a ton of well informed organized obsessives who will be hopping on the phone to book things the instant they can.
Hopefully Fastpass+ never infects Disneyland.
edit: Wait, it sounds like it might have. Well crap.
