In casual speech it’s fine to say things like “You know, I really liked that blouse you were wearing yesterday.” But some people fall into the habit of punctuating their speech with “you know” so frequently that it becomes irritating to the listener. Most people do this unconsciously, not meaning anything by it. If you become aware that you have this habit your friends and colleagues will be grateful if you try to overcome it.
Hip-hop popularized a similar formula—“know what I’m sayin’?”—frequently used when there is little or no doubt about what is being said. It means something like “right?” It’s time to retire this worn-out phrase—know what I’m sayin’?