As a mobile app tester, it's essential to avoid focusing solely on the UI, as this can lead to poor user experience and uninstallation of the app. Creating an in-house testing infrastructure is complicated and may not be cost-effective, with device management taking significant time and money. While emulators/simulators are useful for early development stages, real devices should be used for testing before releases to ensure reliability and effectiveness. Testing everything at once can be overwhelming, so it's crucial to prioritize the most important aspects of the app based on target market data. Randomly testing an app without a strategy can lead to missed bugs and ineffective bug fixing. Finally, understanding the app itself is vital to creating comprehensive test cases that align with user expectations.