Your Google Play listing is the most important factor in your apps ranking. Below are some tips to optimize your Google Play listing and increase installs/downloads.
Title - By far, the Title is the most important factor in how your app ranks. Think of something unique, but that also contains a keyword that you want to rank for. Do some research on Google Play to determine what competitors have named their apps.
Full Description - The Full Description is also vitally important. Try to use keywords that you want to rank for and list your features. Do not overdo it though on your keywords, as it is against the rules to stuff keywords into your description.
Graphic Assets - Good looking screenshots and a cover page can really make your app stand out when a person is searching Google Play. Make sure to provide assets for Phone and Tablet at a minimum. You should also serioisly consider a cover image.
Icon - An icon that looks professional and stands out from the crowd can also really make an impact.
Promo Video - You should always provide a promo video for your app. Still images cannot engage the user as much as a video.