Make it Easy.
Don’t just tell a waiter what you can’t eat. Instead, be proactive. You know more about the gluten-free diet than he does, so don’t make him guess the menu options that might be right for you. Scout the menu for choices that are likely to be gluten-free and present them to the waiter as starting points for further investigation. Let the waiter use his limited time to interface with the kitchen and to confirm that your choice is a safe one.