1. Drink the bugjuice. Last year was my first year (both at the con and drinking the bugjuice) and it was really, really good.
2. For the wemminz: Don't wear heals. Especially if you drink the bugjuice. I learned this the hard way last year.
3. Contact cards. Handles and emails (bring a pen in case you want to give your number too). I don't know about anyone else, but I have a terrible memory and end up writing stuff in a notebook.
4. Socialize! That's why we get together and give these talks instead of having webinars. I've made a lot of friends at DEFCON just by being sociable.
5. Don't be afraid to ask questions.
6. Pack light, especially if you're planning on buying stuff from the DEFCON store (which you totally should). You'll appreciate having the extra room if you didn't have the foresight to bring an extra bag.
7. Sharing is caring.
8. Don't be an asspony.

<3 Totten