Hrm...I would start by gathering a solid core of people who are really excited and committed to the project, and who know about all aspects of theatre production. And who have lots of money. :) There's info online about how to create a non-profit organization- if you do that then you are eligilble for grants.

Finding a venue/home is also an important first step.

I have started 2 companies. It depends on what you're trying to accomplish.

1. Figure out your mission, purpose, goal
2. Write up a proposal for a show or your goal
3. Bring people on board with your project by showing them the proposal
4. Figure out with the people you bring on board to help you what kind of budget you can put together. (Note, in theatre, rarely does one make a profit, in most cases, you are lucky if you break even- however, there are ways to subside that)
5. Set dates for your first production far enough in advance to be able to
a. rent a space that suits the show
b. publicize the heck out of it
c. raise more funds to help you complete it
6. In the beginning, I suggest shows that are popular- that people have heard of so you can build up an audience base.
7. If you're in the bay area, go to www.theatrebayarea.org and order their publications for reh/perf space and publicity information
8. You're likely to get more experienced people if you're wiilling to payy everyone, even if it's just a small stipend.

That should get you started for while.