David's Tip of the Day: Beginner Tips #7 - Beautiful Notes
Now that everything is relaxed and spit isn't running into your harp!... move around the harmonica, making every note played sound warm, full... beautiful.
If you get a little bit of an upper or lower note, adjust and then move on. If a note sounds flat, bent or airy, or the note squeals or stalls (won't sound at all)... adjust your tongue location (usually down). Your goal is to make every note sing with the least amount of effort as possible.
P.S., This is a great exercise for intermediate and advanced players as well. Using bending and other challenging techniques on the harmonica will tend to cause tension and thus poor tone.