Cross-promotion is another useful strategy, particularly for independent companies with little left over money for advertising. "The first cross-promotion we did was with Bolt Creative, best known for their smash hit Pocket God," said Pusenjak. Both developers use some of that precious description space for mutual plugs, increasing users' exposure to both games.

Julian Farrior, CEO of Backflip Studios told an audience at GDC that his games "got major bumps thanks to Apple promoting our game and cross ads from other games." Backflip is responsible for such successful games as Paper Toss and Ragdoll Blaster, with a combined 22 million downloads across nine different apps. Ragdoll Blaster's versions plug Paper Toss and vice versa--if you download any of Backflip's apps, you'll hear about the others.

And of course, sometimes a game just promotes itself. CBS primetime sitcom The Big Bang Theory wrote Doodle Jump into one of its episodes, and The Office's Rainn Wilson has tweeted about playing the game. This kind of free advertising is mostly good fortune, but there are ways to capitalize on that fame.

When the Jonas Brothers name-dropped Doodle Jump as one of their obsessions in an issue of Tiger Beat magazine, Lima Sky opted to buy an ad in an upcoming issue. The Jonas Brothers-themed ad reminded readers that if they wanted to have that much more in common with their idols, they should download the app. It's important to know your audience and take advantage of new and creative ways to reach them.