When someone retweets you, they have two choices: they can just click the “retweet” link to retweet it, or they can create a tweet that comes from them, and adds a credit line (such as RT @user) in the tweets.
And while you can add “Please retweet” to your tweets, I would do this very, very sparingly. It’s often inappropriate or annoying. I use “Please retweet” only once every several hundred tweets, mostly for crucial, time-sensitive tweets.
Courtesy of: Quick Sprout