I agree with Wraith and Orc, its their first event and is free. Whats more, even if they die their first event is a mulligan pretty much. They shouldn't worry to much about the details and just come and relax and see whats up. The first event is always a learning experience so ether way they will walk away confused but exited to come back and do it again (we hope).
I'm not a marshal but ya...
The biggest step is to arrive as early as you can. Being new they need to fill out some paper work and if they are PCing, they need to make a character. Whats more, having the chance to do some newby training is never a bad idea. Try and have some extra weapons for them if you can and remind them of the "dress code" and that they should pack and dress according to the temperature. If your close enough friends, it may even be a good idea to help them back as I know on my first couple events I well over packed. If they want to do archery, they WILL need their own bows/crossbows as Monster Camp is short on those as it is and needs more. Send a message to Adam (dragonfire8974) if you need some weapons. He usually has some extras that he can borrow out. Tell them about how light spells and effects work and have them plan accordingly. Try and get them set up with some form of armor if you can. The first game is always hard, and not having armor makes it that much harder. The rest is fairly standard like waring boots if they have them and such.
Sorry for the longwindedness of this.
Last thing, we are going to try and set up a fight practice for new players so keep your eyes open for that.