As a clean code enthusiast, the design principles I am using in my day-to-day development activities are the commonly well know ones. Since they never let me down, I consider them a starting point and worth outlining.
General
- Encapsulate what varies
- Favor composition (over inheritance)
- Program to interfaces
- Favor loose coupling (and high cohesion)
SOLID
- Single responsibility – a class has one reason to change
- Open for extension / Closed for modification
- Liskov substitution – subtypes are substitutable for their base types
- Interface segregation – interfaces shall be small and cohesive
- Dependency inversion – high level modules shall not depend on low level modules, but both on abstractions
Kaizen Driven Development 