this might help if it's your first time: http://slice.seriouseats.com/archives/2011/08/what-to-expect-at-a-neapolitan-pizzeria.html
and this:
http://slice.seriouseats.com/archives/2013/01/serious-eats-guide-to-eating-pizza-in-naples-napoli-italy-neapolitan-pizza.html?ref=title
Thank you!