Check your bill before you tip at Miami's restaurants and lounges. Many add on a gratuity in advance, no matter the size of your party. Also, if you dine on Ocean Drive, ask for prices when your waiter offers you a drink or food special (it's usually one of the most expensive items).
Order a cafecito (Cuban coffee) at a shop like David' Cafe in South Beach. Just brace yourself for the caffeine hit.