Best practices for securing a mobile application include implementing strong authentication methods, utilizing encryption for data transmission, and regularly updating the app to fix vulnerabilities. Developers should follow secure coding practices, conduct thorough security testing, and perform penetration testing to identify and address potential weaknesses. Additionally, employing secure APIs and validating user inputs help prevent common vulnerabilities such as SQL injection and XSS attacks. Overall, a proactive and layered security approach is essential for protecting mobile applications.