Choosing an agency to develop your mobile app is a momentous decision. There are many factors to consider during the vetting process including: Budgets, Skill Sets, and Preferences. Another beneficial quality of a mobile app developer is if they have adequate knowledge of your business.
If you are looking for agencies to build your mobile app, below are a few things to consider:
Portfolio - Have them provide you with a copy of their portfolio. They should have links to app/games they have deleloped and published to the various app markets to allow you to download and see the quality for yourself.
Mobile App Development Skills - You must hire developers that experience in the platforms that you are considering. If you are developing an Android App, make sure they have expertise in Java, Eclipse, Android Studio, or Xamarin. If you are developing an iOS app, make sure they have expertise in Swift or Objective C. If you want a single app for both platforms, make they have experience in Hybrid Apps or Mobile Web.
Cost and Terms - Pricing usually is based on the complexity of the app you want to develop. The more features you are looking for, the more expensive the development process will be. It is important to look for a balance between cost and experience. The cheapest option is not always the best.
Communication - Communication between you and the developer/agency is vitally important. They must be responsive to your questions and queries. They should provide you updates throughout the development lifecycle and they should also be flexible if the scope of your app changes.