As noted in the other comment, I've tried a lot of different things with varying levels of success, but for the most part working on the product and App Store Optimization have been the biggest things.

I do have a lot of new ideas that I'll be trying over the coming months though. It's a different strategy putting more focus into a bigger app than one off sort of things. Many of them didn't get any outside promotion other than maybe a tweet here or there. 4 years ago the App Store was a much different beast. It really was build it and they will come. As the market matures though, you have to change with it.