Which chord fingering should I use?

I'm using Mel Bay's First Jams for Mountain Dulcimers book, which gives the melodies of each tune (all in DAd) including tablature and chords.  It also contains a CD which plays each tune first with the dulcimer on melody and backup guitar chords, and then with just the backup guitar chords, so you can play the melody on your own accompanied by the guitar chords.  It's great for practicing tempo and rhythm, and also in hopes that I can play with someone else at some point.  I decided it might be fun to try playing the chords as written with the dulcimer melody and guitar chords in the background.  So I went to my chord chart (which I'm really not familiar with) only to find that, for the very first chord in the tune I wanted to play,  which was G, there were four different fingerings offered, and they all sounded completely different to me.  I realized then that there were many fingerings for every chord (again, this is all in DAd tuning), but they don't necessarily sound the same.  So my question is, how do I know which fingering to use for which chord on any given tune?