Rehearse Your Event Before the Final Run
An event is very similar to a show. Try and rehearse a large part of the event in a smaller scale before the final run. You can even ask your suppliers to collaborate with you for it. Rehearsal is possible for many parts of the event.
I held a huge event four years ago. The stage designers showed me a prototype of the stage in their storage three days before the event. A part of what I had in mind could have been unfulfilled, but there was an opportunity to fix things.
Ask suppliers whether any of them can show a small prototype before the final run.
Have a test run of those parts of the event which are related to you. For example, if you have to make a speech, rehearse it before the event, run a sound test, or control the protocols in the entry and exit points.
Ensure the suppliers’ competence regarding the parts you can’t test.