Play softly. Warm, radiant air is what you're looking for. A pro player plays at 40% of their capable volume as their normal volume. So, no sucking or blowing... warm, radiant air flowing through the harmonica.
Full access to all lessons starts at $20/month! (with annual subscription)
After watching the BluesHarmonica.com overview video, try one of the lessons below to experience a lesson at BluesHarmonica.com.