Direct Message over Twitter is the best way to talk with the Twitter followers. But i got to know that earlier it was possible to talk with the non-follower with just implementing small change in the url. The user whom a twitterer wanted to DM used to Change the URL like : http://twitter.com/direct_messages/create/{username} "Here in the user name the twitter whom a twitterer wanted to send the Direct Message used to put his username on it.
By Doing this, a Message Box used to visible with which a user used to DM.
But Now a days this hack is not effective to Direct Message the non-followers but is acceptable for your followers. This happened due to the update of the Twitter's new policy which says that "no DM to the non-followers".