Your approach to the know-it-all in your office depends on your position relative to the person. An interesting article on this topic was published at the Harvard Business Review website.
If the know-it-all is your employee, then you have to provide feedback so the person understands clearly why he has to change his attitude.
If the know-it-all is your colleague, start from your mutual relationship. If you're friends, you can talk openly. However, if you don't know each other very well or if you don't have a good relationship, be careful not to act like a know-it-all yourself. Try to build a closer relationship before you have a talk with him.
If the know-it-all is your manager, the greatest caution is needed. Don't make an issue of it when he behaves as if he's been everywhere and knows everything, if it's not important. In other cases, when it is important to persuade the boss to change his attitude, try the following steps.
1. Ask the right question
Ask your boss if he's ever experienced a similar situation and how he solved it. It's also good to use the "what if" question.
2. Gain more time
Tell your boss that it sounds like a good idea. At the same time, however, ask him whether you could collect more information and opinions by e.g. the end of the week.
3. Point out the risks
If you can see real risks, name them. Say that you want to be sure there are no problems and ask, for example, for a consultation with other employees who are involved in the situation.
If you manage to persuade your boss to change his mind or to consider other options, don't boast about how great you are. First of all, thank your boss.
-kk-