I've never been in a LGS in my life but want to go to the Kaladesh Prerelease. Thing is they explicitly stated they don't do registration and they're sure they can "find a place for everybody"... How does this even work? Don't they have a limited amount of prerelease kits or something?
They do, but if they have a good idea of how many people will come from past experience and thus ordered more prerelease kits than that for wiggle room, then they should have enough. Go ahead and check it out.
On the topic, tips for your first prerelease not directly related to deck building:
* Bring water and snacks.
* Have something to do between matches, or if you have a bye.
* It's generally better if you bring card sleeves. Remember to leave time to sleeve up your cards, though.
* It's a good idea to bring your own lands. The store will provide them, but everyone at some point will forget to give them back. By the way, give them back to the store after the event if you borrow any from them.
* Open up all your packs, throw away the packaging,
then look at your cards.
* It's perfectly fine to talk about your cards with other people when assembling your deck, especially to brag about a Masterpiece you pulled. You can also feel free to ask for advice.
* If anything seems fishy during the match, call a judge.
* This is a casual event, and it's generally OK to take back actions you didn't mean or didn't immediately realize weren't possible, but some players are less lenient than others.
* If a deck isn't working out for you, it's perfectly fine to completely change it between rounds.