There's an even more low-tech way. Teacher starts calling you out on it. A little "ding" from a bell or similar draws your attention to it, when you wouldn't notice otherwise. After a while, your classmates will start policing each other, and even the quiet ones will speak up so they can play the "game" of avoiding filler words.
I had a PM at Google who did debate in high school. In his debate class, everybody would throw a pen at him every time he said "um". He has very precise, articulate diction.
