I am talking about paying attention to the chord progression of a tune as you learn it. Most of my students resist this advice because there is just so much darn work behind the comprehension and application of chord theory. I'm here to say, begin the work and keep it up. It's worth the effort.
Need a place to start? Check out Ken Kolodner's Chord Theory and Mapping for the Hammered Dulcimer ... everything you need to know to master the hammered dulcimer!
After 20+ years I still must work diligently to get the chord work down in a tune. Today, as I review and revive old tunes in preparation for an upcoming intensive week-long Sandbridge workshop with Ken Kolodner, I am finding that those pieces learned with focus on chord progression are coming back much more quickly those learned more by rote memorization. I'm having to relearn those early tunes the RIGHT way!
So ... take note of the way the chord progression is reflected in the melody line - learn how decisions about harmony are made - work on back-up arrangements even if you never play with others! The tunes you work so hard to acquire will stick better in the end.