I tend to know a lot of stuff and used to always blurt it out unsolicited. Basically the know-it-all who unfortunately tends to be right. Now whenever I feel the urge to correct something, I remind myself that nobody likes a know-it-all and just don't say anything. I've gotten decent enough at holding my tongue that people don't really think of me as a know-it-all but still ask me about things rather than, say, using a dictionary or google.