Venture capitalist and e-commerce pioneer Paul Graham gives 13 pointers, including "Get ramen profitable." Huh? See paulgraham.com/13sentences.html.
"Ramen profitable" means a startup makes just enough to pay the founders' living expenses. It's not rapid prototyping for business models (though it can be), but more a way of hacking the investment process. Once you cross over into ramen profitable, it completely changes your relationship with investors. It's also great for morale.