Most of the principles of RWD with which you are already familiar with are discussed by Russ Weakley in this video. However, there is one major difference from your notes and your text. Weakley recommends that we concentrate on content and use progressive enhancement to determine our breakpoints. Both our notes and your text suggested that device widths should be used to determine breakpoints (however Progressive Enhancement is covered in your text at Chapter 9). Weakley's argument is a good one, so incorporate that principle if you can.