Find a computer lab large enough to comfortably fit all of the students in the class. Have each student take a seat, and go to twitter.com on a computer. Have each student make a log in for Twitter. Walk around and write down each student's Twitter name so you will know who is who when the posting begins.
Tell each student to "Follow" the rest of the students in the class. Read out a Twitter name and have the entire class search, find and follow the Twitter name. Tell the students that they are to follow and post on only the names of the students within the class.
Tell each student to post a "Tweet" on something that matters to them, letting them choose a clean, G-rated topic such as a sports team, a movie, a musical group or homework. Give the students time to post their first Tweet.
Tell students that they must "Reply" to each Tweet, and that the post must be positive in nature. Allow students to post questions about the Tweet, or let them make a positive or discussion-based statements about the Tweet. Monitor the posts as the students make them, and monitor the replies as well to ensure that no student is being treated unfairly.
After awhile, have one person post a Tweet question, and have the class respond to the question. This will engage students in conversation through social media instead of through face-to-face discussion.