Eureka! You've come up with a great idea for an invention or a new business. Or you've discovered a niche in the marketplace crying out to be filled. What's the next step?

In a perfect world, you simply set up shop, watch your business flourish and count the money as it flows over the transom.

But in an imperfect world, you need seed money to launch your business. And to get that capital, you'll have to go begging for investment, either from a bank, a venture capitalist, an angel investor or your uncle.

Most of these sources of funds, except maybe your uncle, will want to see a business plan. For many entrepreneurs and Bill Gates wannabes, that's the most difficult part of launching a business: translating your idea, your vision, into a dry little document designed to win over a skeptical investor.

It's even more difficult than closing the first sale for your business.

A business plan has to convince an investor that your idea for a company is solid and that you're the right person to make the whole thing work.

Venture capitalists and successful entrepreneurs stress that the best business plans should be short — and simple.

Extensive financial projections aren't needed. Clarity about the startup's product or service is.

"The first piece should be an executive summary," says Shanda Bahles, general partner at El Dorado Ventures, which backed EarthLink and a variety of other technology companies.

"Think of it as a calling card to get you in the door, to get me asking questions. Do not write a 50-page business plan with five-year financial models. It's garbage in and garbage out."

"It should be two pages," declares Stuart Reid, co-founder of Urban Communications Transport, a startup broadband provider in New York City. "If you can't say it in two pages, you can't do anything."

Obviously, investors want to know the ways in which you plan to build the better mousetrap. But venture capitalists will be most interested in the people behind the product.

"The management team is key," says Reid. "Investors invest in people, not ideas. You've got to pull a strong team together."

"Investors are always going to look at management," says Thomas Cooper, a doctor who has started four successful businesses in the medical field and teaches entrepreneurship at Columbia Business School. "Who are these people, and can they pull it off? What are their backgrounds?"

A good business plan isn't stuffed with financial projections, but it does explain how the business will make money.

"The most important thing is sales," says Cooper. "If you can't get someone else to open up their wallet and turn money over to you, it doesn't make any difference how great the idea is."

Cooper wants details on how an entrepreneur is going to close the first sale, how many sales he or she can make in the first year and how long it will take to close those sales.

Finally, a good business plan should not be a formulaic, fill-in-the-blanks document that looks squeezed out of some cookie-cutter computer program.

Chip Hazard, a general partner, says he'd much rather see an entrepreneur's fire reflected in the executive summary.

"The passion that an entrepreneur has is fabulous," he says. "It's a burning desire to change the world. You love that when that comes through."