I'm highly ranked on organic search (#1 for most terms), have paid ads, pursue articles when the opportunity arises (these have historically helped a lot), limited giveaways, and watch google alerts for mentions of the app and respond as appropriate. The main app is generally in the top 30 grossing for its category, and I've found being high in that to be self-reinforcing. Being in the primary field the app is for has definitely helped since I have friends and contacts there.
One notably potential source I have not really pursued much is social media, Twitter in particular. I'm one of those people that pretty much never uses it and doesn't understand the allure.
One notably potential source I have not really pursued much is social media, Twitter in particular. I'm one of those people that pretty much never uses it and doesn't understand the allure.