We had an expression in the camera store where I worked in my youth - - - REFM - - - pronounced "ree-fum." It means "read your f***ing manual." We never said this out loud to customers, of course, although we surely wanted to while answering an endless stream of questions that are covered in the first few pages of every camera manual. We also use refm as a noun, as is "The refm's back - I'm taking my break before he corners me again."
So, you should always refm, or at least page through it, but you never want to become a refm in the eyes of your camera store.