Study and research the area you want to invest in. Know that area inside out - Join business organizations, befriend the local city commerce. Find out what's high in demand. Research potential customers and clients for needed/innovative services.
Try investing a small amount to begin in the stock market . . . wisely and conversatively of course. Build an investment portfolio. Develop an expertise in which you excel, and turn that into a niche. Be wary of investing in markets where there is a oversaturation of individuals already working in that area, because it is much harder to break into it.
And then start saving towards it - set up a savings account dedicated to small business. Go to seminars, events, or activities which teach you more about how to not only start a business but how to be successful in that particular business. Travel to various conventions, fairs, etc. where organizations of people working in the area are involved. Read discussion boards or forums dedicated to that particular type of business - you'll often get info from these sites which you won't find in classes or textbooks.
Make a basic business plan, think about your goals, etc. Learn business mgmt. and discuss with business leaders and other innovators what you should and shouldn't do.
In other words, learn the ins and outs of the product or service you're interested in, and the industry. Social network - sign up with LinkedIn or other business or professional social networking sites and find people who are players in the field.
In any case, become an expert in what you want to do, know it inside out, and chances are, you'll have a better chance of finding a niche which you can turn into a successful business, small or large.
And as Norton said, don't be afraid to fail, many times before you succeed.