To prepare for an interview on Object-Oriented Programming (OOP), focus on explaining core concepts like OOP itself, which is a paradigm based on objects and classes. Be ready to describe **inheritance**, where a class derives properties and behaviors from a parent class, promoting code reuse. Also, understand **abstraction**, which involves hiding complex implementation details behind simple interfaces, and have a coding example ready to illustrate this concept if asked. Practice delivering these answers clearly and confidently.