Without additional context of what you're trying to build: talk face-to-face with people and stand over their shoulder as you walk them through the signup/first use process.
Though neither sufficient nor strictly necessary, willingness to pound pavement for your first users appears be highly correlated with traction. It's the quickest way to find out how people will actually play with your product.
Start with a niche group and personally reach out to them with an amazing product. For example, Facebook was for Harvard Students only. Airbnb started getting hosts and guests in only New York. Ben Silbermann of Pinterest began by recruiting users manually by literally walking into cafes in Palo Alto and asking random people to try out Pinterest while he gathered feedback over their shoulders.