SOLID

Single Responsibility Principle (SRP)

A class should have only responsibility.

Open Closed Principle (OCP)

Open for extensions and closed for modifications.

Liskov Substitution Principle (LSP)

Base class objects can be replaced by child class object.

Interface Segregation Principle

Don't force implementation methods which are not needed/used by child class. Use smaller interfaces.

Dependency Inversion Principle (DIP)

High level modules should not depend on low level modules. Use Abstract layer in between.