Surround yourself with people who have done it before. Not consultants, not coaches, people who have walked the path you are embarking on.
The good news is that the startup community is the most helpful business community of any industry, by miles.
I'd be happy to do a call to help you figure out how and where to identify these supporters and champions. Good luck!
Fun book: Upstart Startups by Lieber. Also read The Go-Giver by Bob Burg & John David Mann.
Definitely seek out mentors who have traveled the road before you. I would also recommend an executive coach, but of course I'm biased there. :)