One of the most basic aspects of proper use of object oriented programming is to properly design your classes in the first place.
Designing a Class

One of the first things you need to learn when you start on Object Oriented Programming is about classes and objects and what the difference between the two is.
What is the Difference Between a Class and an Object?

One of the big benefits to Object Oriented Programming is being able to define classes that can be reused from one project in another. A class library takes this even further by providing a prewritten set of classes that can be used in all your projects.
What is a Class Library?