Two details cause more day-of problems than any others: what a guest cannot eat, and where the tables go.

Allergens

Allergen information travels with the catalog item, so a menu built in a proposal carries its restrictions through to the kitchen without a re-keying step.

Floor plans

Attach the room layout to the event so the captain and the rental order agree. A layout that only exists in someone's email is a layout that will be wrong.