Not meant to be blunt, but there's a really obvious way: make the game better. Make it stand out visually, gameplay-wise, make sure people share your app (you could ask them to rate it, you might give them something in return), make people want to get back to your app. Create promotional images and submit them with your app so that your app can be featured when the Windows Store team thinks it's good enough. Listen to your users and fix their problems.