I travel for work and have had the luxury of visiting quilt stores in a few different states and like some more than others because of something they offer or do differently than others. For example:
A large room for spouses that includes a large tv, pool table, and large comfy chairs. That same store has dedicated space for children with toys and chairs.
The pattern, fabric, and supplies used in every displayed example, which would be rotated often. I've seen samples I wanted to make but the shop didn't have the supplies.
An electronic newsletter auto sent every month.
Easy, medium, and advanced samples.
A large table that could be rented to layer a quilt. Many people don't have a comfortable space to do this in their home. By providing the option to rent the table, customers could feel a sense of ease if some or all of the fabric in their project wasn't purchased from the shop.
Involve customers with selecting the type of fabrics sold.
Open during the evening at least twice a week.
A color wheel for use by customers.
A sign stating fat quarters can be cut.
A monthly sale or special.
Classes, talks, how-to's, demos, etc
A regularly maintained website, believe it or not I know of a store that doesn't have a website.
A brag page on the website with photos of customers.
Charm packs
Fat quarters displayed with the bolt
Muslin
A large selection of backing fabric
Finally, I'd keep "trendy" items to a minimum.