a few points from a recent festival.

Lots of signs & make sure everyone in a position of apparent authority (gatekeepers/ticket sellers/wandering security folks/committee members/volunteers) know how to find out what is happening.

A washed out venue did not have a re-direction sign, nearest gatekeeper didn't know said venue was washed out, ticket sellers didn't know either, several performers didn't get to the replacement venue ... but an organiser had written the new venue on a small blackboard near the ticket sellers!