Its really about being a photographer, rather than a painter. Really check the sound in the cutting room before going back behind the desk (or mouse).
I sometimes do the old "cover 1 ear" and walk around the harp and see where its projecting what frequencies. I'd stay nearer to the harp, or do 2 sets of mics. Watch out for the reflection off the music stand if used. Also, watch out for non-harp noises like chair squeeks, and clothing rubbing which can be bad. I actually had a few harpists that had pickups on the instruments (so they could play weddings, I guess) and when I used a good (radial) DI, it added a nice bit of clarity. Not at all like a DI acoustic guitar.
I'd also go for a clean and vibeless PRE (think grace, etc...) because harp has resonances that can without warning make a pre get crunchy. Kind of like recording a gong, where the level is 10 Db from clipping, but something is still distorted because of the harmonic richness.
Well, have fun.
tp
www.thomaspmusic.com