Do= get to know him ask about his favorite interests or something find the things y'all have incommon w/each other Wear= depends on what type of guy he is if he's a like rich person definitely wear something classy but if he's a popular person wear something cool like jeans and other types of tight clothing. Usually most guys would say where their taking you but if they don't don't worry always have a backup such as having a change of clothing to fit the occasion.
The best thing to do on your first date is to be yourself and not try to be someone else. You need to be comfortable too so as to be able to enjoy the date. There is also the need to dress in something comfortable like a simple dress with minimal makeup and accessories. You can get more tips at http://www.wikihow.com/Get-Ready-for-a-First-Date-(Teen).