Nisan Gabbay's blog on technology startup case studies is an excellent source to help entrepreneurs understand what works. I've used his list of "Top 7 indicators of consumer internet success" post with one of my clients and found it to be a great conversation starter. How many can you hit?
My favorites are #1 (define an reviously unrecognized niche) and #7 (story that lends itself to mainstream PR).
#1 is all about focus. If the real estate mantra is "location, location, location", a startup's should be "focus, focus, focus".
#7 worked really well when we were starting Destiny Software in the 90s. Rather than running up big advertising budgets, we found ways to engage the press that got our story circulated in all of the trade press. The key is to find an angle in your market that is new or different - editors are always hungry for interesting twists.