Haven't been to Hackathon but Defcon.
This is just my personal guide upon arrival:
1>Turn OFF wifi
2>Turn OFF bluetooth
3>If someone touched me, check immediately if something strange attached.
4>Never connect to Defcon Wifi,
5>Make sure my dial tone is mule if I have to call,
6>Make sure you have fun. Most people there are nice and knowledgeable.