I usually look at the number of days I'm going, try to determine what entertainment is happening that I don't want to miss and lay it all out on a calendar for each day...then make my reservations around that.
If I know I have nighttime entertainment I want to do one day, I'll do a TS lunch and grab snacks in the evening...or a corn dog, etc.
If I know I have mid-day things I want to do, like take a tour or see Aladdin, I'll do a TS breakfast or dinner that day.
And yes, budget / menus can help make the decisions, too...breakfast/lunch is sometimes cheaper, or maybe I like a certain restaurant's dinner, but not their lunch, etc.