What should I know before starting a mobile app development project?

[penofmastery]

I'm planning my first mobile app for a small service business, and I want to avoid costly mistakes. While searching for different development companies, I came across Inovio Soft, but I'm not looking for promotions—just honest advice from people with real experience. What should I expect during a mobile app development project, and what features or planning steps are most important? I'd really appreciate serious suggestions before I move forward.