In my (private) high school's health class "like" and "um" and others were referred to as "stop-words" by the teacher because people would say them instead of pausing. It's really obvious once you look for them, for instance here with pg but anywhere really. I remember hearing college tour guides that would literally say "um" after every single sentence, probably unbeknownst to themselves!
Almost every class in the school had projects, and the health class project was for us to remove the stop words from our speech by the end of the semester. We did this by all using recording software (had to submit either by cassette tape or wav/mp3) and answering questions such as "Do you want to live forever and why or why not?" by speaking for at least 5 minutes. These were our homework assignments maybe once a month, with the overarching goal considered as the class project.
We had to very consciously never use any stop words. We could pause the recorder if we had trouble thinking of what to say, but we could never say those words.
I was skeptical of the assignment at first but my class all agreed by the end of the semester that it made us much better speakers, simply learning to consider our pauses instead of filling the silence with "like" and "um".