The importance of cross-promotion.
We came across a blog post by FIPLAB Ltd., the gaming company behind Talking Gremlin, that puts the importance of cross promotion eloquently:
Lesson #14: Start building up a cross promotion network
If you are serious about building an App Store business, you can’t rely on making millions from a rare, one off hit. You need to plan for the long term and reduce the risk with each subsequent app you launch. The best way to do this, and pretty much essential these days to be able to get a good ranking on the App Store, is to implement a cross promotion screen throughout all your apps. This will eventually allow you to direct thousands of downloads to your new apps as soon as they launch.
Visibility is critical to success on the App Store and downloads = visibility. The more sure fire ways you have of generating downloads without having to spend money on marketing, the lower your risk (and cost!) of failure.
Like FIPLAB, we see cross promotion as one of the most effective ways to advertise your games. Here’s an example of one of how this works:

Because it’s games promoting other games, users respond positively and it performs better than traditional advertising. On the Chartboost platform, you can customize your cross-promotional ads so they’re fully integrated into the look and feel of the app, just like the ones shown above.
Plus, with our fully-transparent analytics you can track impressions, clicks, installs and define frequency caps to make sure it’s always a good experience for your user.

Last, but not least, cross-promotion of your own apps is totally FREE on the Chartboost platform!
About ChartBoost:
We are a technology platform that provides app developers tools to effectively manage their distribution power. That often includes promoting other internal games and promoting other games and monetize that traffic. Our ad server platform combines both in a real time dashboard where different campaigns can be combined and launched on the fly.