Hackathon Playbook Part 2: How to Organize an Event
lob.com
lob.com
The other points are all valid. I'd add that sponsors should be aware of point 8 from the get go. If you sound like a pushy sales guy trying to add your company's API to "hacks" that don't need it the attendees will remember your company for the wrong reasons. If you have product development, pitching, or technical experience that applies you should share it.
This has been my experience at both HackDuke and PennApps with the additional issue of favoritism towards students from the host college.