I'm not a Grad student, but I've been asking a lot of the same questions. Here's what I've found out so far on another forum.

- Having a good advisor is crucial.
- Make sure you're comfortable around your lab mates. You'll be dealing with them a lot.
- Hard work is meaningless. Results are what matter.
- Don't be afraid to speak up and ask for help, or to fail. It happens.

I can look up some more details if you want. I'm looking into it myself for my eventual history degree.