First. Do something you are passionate about. Next, register the business name through a fictitious name statement. You do this in your local paper, the ad will run for about 4 weeks in the legal section. Then obtain a business licence through the county clerks office. Then do some advertising. You can do this for free on sites such as CraigsList. Make up some brochures and see if you can place them at business's where potential clients might go. Try to network with similar business's. Most important..be a man, or woman of your word. Your business will rise or fall on the references of clients. be prompt and responsible, do what you promise. If you offer a needed service at a fair price and people know this, the sky is the limit. be patient and never give up...
Good Luck...I know that starting my own business was the best thing I have ever done..