First of all have a look round for sources of borrowing money. The first obvious step is your bank. They are unlikely to lend money unless you have at least a deposit of 20%. Similarly if you approach the Small Business Bureau and ask for a guaranteed loan they are probably going to want a similar deposit.
They may be able to offer you some advice though. Your best bet is to get together a realistic business plan with what you wish to do and what it will cost in quite detailed format. Also include details of whom you expect your market to be and how large this market is.
A venture capitalist or angel investor is pretty much out of the question unless you have a really unique protected product or a very well established business.
Another source of business funding help may be to apply for a grant. They are difficult to get and you will have to have, not only a good case but a very well defined business idea.
So if you are capital poor the best advice is to start small. Look at a smaller version of what you intend to start up. If you want to open a restaurant for example, look at event catering, cake decoration or providing manned bars for weddings etc. Make sure you have the right licenses, permits and health certificates first.
If you are looking at providing any kind of service start with offering your services to local businesses first and working from a home office.
If you are looking to sell products or hand made items, then start with a mall kart or stall in a flea market, boot sale or local market place.
You can also try eBay, CraigsList etc.
If you looking to sell produce then try your farmers market.
Start small and you have not risked too much and build up. If you do well you will learn, establish your business name and build up capital and customers.