Make sure that every customer-facing member of your staff is as friendly and inviting (and well-dressed!) as possible. It's also important to ensure that each member of the staff is well aware of the restaurant's core values and represents them when interacting with guests.Check out the local competition to discover what they are neglecting in their customer experience, and then offer it in your restaurant. Something as simple as offering a free bottle of water to each customer could win you extra brownie points.
