Regardless of platform, the app store is a developer's way of reaching millions of people around the world. Those people speak a variety of languages and as such desire an app that's tailored specifically for them. Others have offered tips on localization before, but here's some tips from an actual developer in the localization trenches.
The Amazon Appstore Developers blog invited Playrix' Head of Marketing and PR, Dasha Kobzeva, to talk at length about the process of localizing apps for the Amazon Appstore. The advice is meant for developers of Kindle Fire apps, but developers on all platforms should heed the advice.
First and foremost, Kobzeva says developers need to pinpoint their markets. Localizing an app in every language is foolish and wastes resources. Developers need to find which markets bring in the highest downloads and monetization rates. From there, localize for those markets. If you don't have time for that, at least localize your descriptions and screenshots.
If you are going to localize everything, be sure to put considerable thought into the title. Kobzeva says that a good title that can be understood across different territories doesn't need to be changed. A specific title that plays towards a very specific culture, however, would need to be changed so players in other countries can understand it.
Like in traditional film and game localization, events in your app may need to be changed to resonate better with a foreign audience. To better help those localizing the app, Kobzeva says that developers need to provide as much contextual information as possible. Many Japanese games in the 80s suffered from poor translation because the localizers were handed the finished game and just told to translate the text. There wasn't enough information in the game to provide adequate context and the localization suffered for it. It's now 2012 - you can provide translators with more than enough information to make a localization stand out.
Finally, Kobzeva stresses that a "bad localization is worse than no localization at all." It's suggested that developers carry out their own internal QA sessions to determine if a localization is up to snuff. Such tactics can help prevent embarrassing localization mistakes that can cost you customers.
Of course, Kobzeva works at a large developer who can afford professional localization services. Not every developer, especially smaller indie developers, can afford this. Localization is something that you should only tackle if you have the resources. Developers can, however, push their games onto app stores in other territories, and just hope for the best. Foreign apps can gain traction and become popular in other territories if the content can get across the language barrier. Art and music apps come immediately to mind, but good developers and artists can find ways to speak to people regardless of language or culture.