Husbands and wives, parents and kids, and friends do it, and it's often joked about or considered endearing, but nagging can take a toll. By definition, to nag is to find fault incessantly, or be a persistent source of annoyance or distraction. If this tactic worked, it's doubtful that the American Cancer Society (ACS) would list nagging as something not to do when helping family or friends quit [source: ACS]. Smokers may even go for a smoke as a way to escape the repeated verbal noise [source: ACS]. Cigarettes can become the needed friend while the nagger becomes the enemy. If you have to ask your roommate to pick up his wet towel -- on average -- seven times every day before he does it, for example, and this has gone on for years, your nagging hasn't produced a change in his behavior. Nagging repeatedly about smoking probably won't be any more effective.