How do you choose a good app development agency

Hi everyone, I’m planning to create a new app, but I’m a bit unsure about where to start. I’ve been looking into different app development agency options, but it’s hard to know which ones are reliable and experienced. Have any of you worked with an app development agency that made the process smooth and easy? I’d really like to hear your experiences, suggestions, or tips on picking the right app development agency without running into problems or spending too much.