Learn

What design patterns are and why you should learn and use them
Understand and apply important design patterns such as the Template Method, the Strategy, the Singleton, the Facade, and the Factory Method
Identify and avoid anti-patterns—for instance, using God objects or having a so-called pattern fetish
How and why to design modular and extensible code by exploring important SOLID principles
How to quickly refactor code that does not adhere to design best practices by using your favorite IDE