When you go to a restaurant, it is difficult to keep everyone happy, but it is not difficult to make them dissatisfied. Taking too long to take on order, constantly forgetting customer requests, bringing the wrong food or not showing up for a few minutes. All these things will make the customer experience a bad one, and they will remember it. People remember how they felt and not how good the food was.
Keep it simple. Give customers the attention they deserve. Confirm that you have the right order. Check in regularly to see if everything is OK. A few simple rules that will keep customers happy most of the time. Now that you have the simple rules, find people that can execute them easily so they can save their effort to go the extra mile.