I feel the second most important principal behind Interior Design is Rhythm. This also includes Repetition. This could include the same finishes featured through out a space and also repeating the same pendants over a kitchen island. The sense of rhythm can help connect a space which when designing open plan living is vitally important. As you can see in the image below from Houzz UK by Concept Interiors, similar tones in the textures, colours and fabrics are used throughout. Splashes of yellow in each space tie all the areas together. The same wood in the kitchen is then featured on the flooring in the living area all allowing the rooms to flow.
By following some of these simple principals when designing your space really can provide the wow factor.