Then do a business plan. Figure it out according to your specific case, looking at what suits you, what matches your strengths and weaknesses, what you want out of the business, what resources you have, and many other questions.
That's why people plan before they start. Every plan is different, just like every person, and every business. Find your own best way.
Tim Berry is the chairman of Eugene, Ore.-Palo Alto Software, which produces business-planning software. He founded Bplans.com and wrote The Plan-As-You-Go Business Plan, published by Entrepreneur Press. Berry is also a co-founder of HavePresence.com, a leader in a local angel-investment group and a judge of international business-plan competitions.