A few words about app design
If you're thinking about app design, then you're actually thinking about UI/UX design. User interface and user experience design are integral to the development of all apps – from the most basic to the largest and most complicated applications. UX design defines the decisions that structure the user experience – the app structure, types and number of screens, screen flow, etc. UI design is all about designing the actual user interface – color spectrum, button size and types, fonts, and more. High level UI/UX design complements the app development, and gives the code a beautiful look.
App design – what should you keep in mind?
App design is a skill that not all designers possess. So, before you approach a design studio with your app idea, make sure that they specialize in UI/UX design and that they have the track record to show for it.
Make sure that the design matches your app development characteristics, and especially your designated operating system (iOS, Android, or both).
Make sure the app design adheres to both aesthetics and functionality. At the end of the day, the design is meant to make things easy for users and to help the app become a success.
Your app is an extension of your brand, so it has to speak in the same language your brand speaks (colors, fonts and all other brand assets).
Most importantly: Request to be actively involved in the design process. Ask to see design wireframes. Conduct brainstorming sessions on the different screen mock-ups. Don't be afraid to ask questions. Remember: Do not authorize the design unless you are 110% satisfied with what you've seen.