I would try to maximize impulse buys. It's amazing to me how many stores don't sell fat quarters, or who don't display them nicely. Lots of times I'll go into a quilt store, not because I "need" something, but because I like to look in them. I'm much more likely to buy something for my stash if the fat quarters are in cute arrangements near the bolts of fabric, rather than stuck in a corner somewhere. Kits are another thing that I know people pick up on impulse.
I think I would try to make a niche for myself...that is distinguish myself from other stores in the area...maybe carry more modern fabrics, more batiks, more something than the other stores do...that is have a little bit of everything, but specialize in something. It annoys me when I go to three stores in a city and see the exact same fabric featured in all of them. I know that there are tons more fabrics out there, I can't figure out why they all carry the same ones.