In some levels you have to compete for tips with another waitress, I think this level is very funny and quite challenging as well. Sometimes you can get a hint on which skill you will need in a certain level if you pay attention to the opening screen before you begin to play, it will say something like 'customers will only seat on chairs that match their outfits.' In other instances what will help you get ahead is to match the color of the customers' outfits to the color of their chairs. In some instances speed will help you the most taking care of customers fast and not chaining will be key. Some will help you more than others depending on which level you are playing. Different things will help you along the way, like chaining, color matching, serving drinks, keeping hearts full etc.
There is more than one way to get and expert score in all levels.