This is a cross-post of my answer to a question posted on Quora:
A few thoughts..
Rovio’s strategy for its first Angry Birds release was largely dependent on developing a high quality product (with the assistance of their game publisher, Chillingo), and finding success in the Apple app store. Its first app store rankings were driven by distribution to Chillingo’s Clickgamer audience and “Game of the Week” featured placement in the app store.
Rovio intentionally developed Angry Birds game to be broadly appealing and not niche-focused. They also made it quick to open—to make the game attractive to people with only a few minutes to play via multiple visits.
They hired a game publisher, Chillingo, who provided them with a social platform (Crystal) to improve retention and engagement by allowing users to challenge one another. Chillingo distributed the game to its audience of players under their Clickgamer brand. Chillingo also had strong ties with Apple, which it leveraged to get the game featured on the front page of the UK App Store as “Game of the Week.”
Rovio’s subsequent launches included additional acquisition techniques—they heavily leveraged the Angry Birds brand, and they started building for fragmented distribution: they are on most kinds of platforms and social network —Chrome, Google+, Facebook, iOS, Android, etc. They also used paid advertising when expanding to Android (AdMob).