Octodad, initially a student project and now the reason for Young Horses' existence as a studio, know all about spreading the word about an indie game (and probably a lot about crossing their fingers and hoping for a hit).
Programmer Kevin Geisler breaks down the Octodad media timeline on the game's official blog, noting that traditional events such as the IGF and GDC aren't huge draws for traffic. Octodad gets a break when other mediums pick up the story: The first major spike was a random note in a Ctrl+Alt+Del comic in 2010, and later from a swath of YouTube "Let's Play" videos. The "other" forms of advertisement even eclipse attention from established news sites, such as this one, at least in terms of traffic to the Octodad site.
The top YouTube videos for Octodad-flavored content come from outside sources, with Cr1tikal's 2011 gameplay video topping the charts at 1.5 million views. The top official Octodad video comes in at 430,000 views. Reddit, Twitter and Facebook are of course important draws, and Octodad finds itself in a lot of forum threads that mention similarly eccentric games, such as QWOP and Surgeon Simulator 2013.
For an overview of how Octodad does it all, complete with graphs and figures, check out the full blog post. Octodad 2: Dadliest Catch is set to launch this year for PC, Mac and Linux.