Don't! John T's comments earlier on in this thread are quite correct. Often several systems on a cb, some electrical systems are picky about how they are powered up or down, cbs get mixed up....I could go back on.
I remember a trainer in a previous airline who thought he was far smarter than he ever really was. His command training trick was to reach up to the overhead panel and switch something off/on that shouldn't be whilst the command cadet was looking elsewhere 'to make sure he was constantly checking things'. Think he hit the ram air one once. Stupid behavior from a 'trainer' who would have had a limited understanding of systems anyway.
Always have a healthy suspicion of your ability to cock something up.