To refactor a legacy codebase, start by understanding the existing codebase thoroughly. Identify the key functionalities, dependencies, and areas that need improvement. Create a comprehensive test suite to ensure that the existing functionality is not compromised during the refactoring process. Prioritize the parts of the codebase that are most critical or most frequently used.

Next, break down the refactoring process into smaller, manageable tasks. This could involve renaming variables for better clarity, extracting reusable code into separate functions or classes, or restructuring the code to follow best practices and design patterns. Make sure to refactor incrementally and test the changes at each step to catch any potential issues early on.

Communicate with team members or stakeholders about the refactoring process to manage expectations and gather feedback. Document the changes made during the refactoring process to help future developers understand the codebase better. Finally, continuously monitor the performance and functionality of the refactored codebase to ensure that it meets the desired standards and remains maintainable in the long run.