Choose a common word at random. Examples of good choices include common words such as “and”, “is”, “or”, or “I”. The author chose “and” for this exercise. If you type a lot and don’t go anywhere, you should probably apply this exercise to typing. Otherwise, stick to avoiding the actual word in conversation. For me, it was a lot easier to make mistakes as I was talking because I tended to think less about what I was saying, versus what I was writing.
Every time you make a mistake, you should do a chore you don’t really want to do, like the dishes.