I think the answer depends on your startup. Social startups have a nice advantage in usually having a viral mechanism. Anything that's sufficiently better than

I think the answer depends on your startup. Social startups have a nice advantage in usually having a viral mechanism. Anything that's sufficiently better than what's already out there will often be something that people want to tell their friends/colleagues about. That's reliable, but from what I've seen word-of-mouth does take a bit longer than most people would expect. There's countless ways, but none can guarantee large volumes of traffic unless you have a similarly large budget. This is part of what makes starting a startup so difficult.