Tips from Google for successful mobile development
As part of Google Developers Agency Program we are proud to share with you The Outsourcing Playbook (for Android development): A Companion to The Secrets to App Success on Google Play. We have found the book to be profoundly helpful and useful, and we hope you will learn a lot from it as well.
Quote from the introduction to the book:

"We've seen a wide range in the quality of apps built with the help of an agency. Getting it right is not only about finding an agency that fits well with your organization and its goals, but also building the appropriate skills and culture in your own organization. This playbook will help you do that with its advice, questions to ask, and tips for selecting and working with an agency to build a high quality Android app."