I'm not being a very good Christian...?

Question

In the last year or so I've developed a really bad habit of swearing and occasionally saying vulgar things in a joking manner. When I'm around other people, I would really like to be a good example of a Christian, but sometimes it's like I just blurt things out even if I'm thinking at that very moment that I shouldn't! How can I clean up my act and learn to control my language around others?