Playing softly - this is huge!
Dave's latest tip on practicing playing softly: http://www.bluesharmonica.com/practice_playing_softly
is one of the most important things a harmonica player can work on.
Playing softly not only keeps your harps working longer, it gives you control over the harmonica - you have to learn how to get bends and other sounds with finesse instead of force.
Playing softly also gives you somewhere to go. If you play loudly all the time it can get monotonous. But if you start at mid-volume, you can go down or up in volume for dramatic effect or to vary intensity.
But when you're playing with a band, you may play hard because have trouble hearing yourself or out of sheer nerves and excitement. Calming nerves is a study in itself, but the simple solution to hearing yourself is to put a finger in one ear while you play. Playing harder generally won't really make you much more audible to yourself anyway.
Getting your band to play softly is also a worthwhile study. Sometimes you get the ego-driven guitarist who just won't turn down.But often it's just a matter of communication. Last week at the Harmonica Collective, I watched RJ Mischo, who tours by using pickup bands wherever he goes, do a masterful job with a young band who only minutes before had been making a mishmash of sound, bringing them into focus and playing softly behind him. The result was a real treat, but the process itself was fascinating. Often he does it simply by starting the song on unaccompanied harmonica, giving them the tempo and the groove (and the volume along with it), telling them to come in on the IV chord.