If you really like someone’s tweet and want others to know about it, you can retweet it. It’s as simple as re-posting what someone else has already written, but if you want to stay on your followers’ good sides, then you’d better stick to the formula. The standard retweet (RT) method is to start a new tweet with “RT @username,” which signifies that it’s a retweet and gives the original twitterer credit for the tweet. This is then followed by the actual tweet. Simple as that. There are plenty of third-party Twitter applications, such as TweetDeck and the iPhone’s Tweetie, that feature easy, one-click retweeting, so all you have to do is click a button and the retweeting is done for you.
Update: Twitter has recently instituted its own formula for retweets. Clicking the “retweet” button from the Twitter website (or any of an increasing number of apps that support the new method) posts that tweet to your followers’ timelines with the originating twitterer’s avatar instead of your own (presumably to keep people from stealing credit for others’ tweets). Twitter’s method is likely to become the new standard, so it’s probably a good idea to follow along.