ECommerce Hack Day - First hack event, what to expect?

Hi guys, I'm attending the eCommerce Hack Day- I'm extremely excited to get out there and build something! I'm still pretty anxious, I'll be flying for the second time out to NYC alone to participate in my first real event- on a side note, if anyone is interested in meeting up feel free to shoot me a message.

I was wondering if any Hackathon veterans could help set my expectations? What will the event be like? How do teams typically form? What role would you suggest I play on the team?

And other advice!

I've got strong web dev skills in Python(Django & Flask), JS( jQuery, Backbone, Underscore, D3), HTML, CSS, PHP. Basic RoR. Limited skills in databases- SQL, !SQL

My best quality is my versatility and ability to learn at breakneck speeds.

Thanks!