1. Clarify what you plan to do.
(…) How will you actually make money at this? With some businesses, it’s obvious: you’re going to sell a product. With other great ideas, it’s not so clear. Where will the money actually come from? What will the costs be (roughly)? (…)
2. Find a mentor.
(…) Schedule a meeting. If it’s a local businessperson, take them out to lunch. If it’s an online person, ask them if they have time to talk at length on IM (better) or by email (if this is the only option). Be persistent, but not annoying - if they say no, ask if you can try to schedule again in the future. If you still get a firm no, send a gracious response and let it drop - don’t make a nuisance of yourself and respect that other people are very busy. (…)
3. Do some honest soul-searching about passion.
4. Do some market research.
5. Write a detailed business plan.
6. Talk to your “inner circle” and make sure they support you.
7. Revise your detailed business plan.
8. Learn how to live frugally.
9. Build up the capital you need.
10. Make sure you have a safety net.

This list has been severely abridged. To read the full list, view the original post at it’s source:
Building a Foundation: Ten Things To Do First If You’re Looking At Starting Your Own Business (TheSimpleDollar)