If you want visual guidance, look at the first couple of minutes of this video (from a Verona performance earlier this summer) - the cameras wander through the crowd and you see how people dress in the different sections:

http://youtu.be/WC2EaceLfFE

(the Balllo performance is a traditionalist park-and-barker, not to my taste and with typical Verona casting, although Meli will be seen in four days in the new Salzburg 'Trovatore' with Netrebko and Domingo(!))