What goes wrong on event day, and how do I prevent it?

The same six things, at almost every event.

1. Venue access is later than promised. Confirm the bump-in time in writing with the venue, not the client. Ask who will physically be there to let you in, and get their mobile number.
2. Power is not what you were told. Ask for amps, not "there's power." Ask how far from where you will be set up. Bring your own extension cords and a generator plan if the answer is vague.
3. Guest numbers change on the day. This is why your contract needs a final numbers date — typically several days before, after which numbers can go up but not down. Without it you buy for 80 and cook for 62.
4. The cold chain breaks in transit. Pre-chill your coolers, load cold last and unload it first, and probe everything on arrival. Log the temperature. If it is above 4°C, you have a decision to make, and you want to make it at 2pm rather than discover it at 7pm.
5. Someone's allergy meal goes missing in service. Prepare it separately, label it with the guest's name, carry it to the table separately, and hand it to them directly. Never let it join the general service line.
6. Nobody knows who decides. Name one person on the run sheet who makes the call when something slips, and tell the whole team who that is before doors open.

Write all of this into a run sheet with times and names, and give every staff member a copy. Most event disasters are not disasters — they are two people each assuming the other had it.