...some great input here...I've enjoyed reading...
One point I have not seen emphasized a lot is to put the "L" in LDS. Being a local expert on diving has to count for something. Run trips, host social gatherings at the shop, or nearby, or beach BBQs.
It's amazing how popular our dive outings became when we started having a BBQ at every one. I bought a portable Weber grill and bring it to all outings, with a cooler of burgers, dogs, steaks, seafood, etc.
Education. Annually, we provide some free, or near-free educational seminars, often coupled with dive events; air management, equipment maintenance, photo stuff, drysuit maintenance/repair, DIR, etc.
Specialty courses. We try to annually offer courses that might not be possible through other shops. I now the states is tight with liability, but a regulator service course is a nice offer. Hosting this kind of thing would be valuable for some of your divers, but might cut into your business if you host reg or tank inspection courses. You''d have to look at that balance.
Bring in guest instructors for DAN courses, PSI, tech, photography, etc.
Our population is really transient (expat) so in that case, we need to always be attracting or creating new divers. For this reason, in our context, I see OW as a vital course. It keeps the life blood of new divers coming into our group, and hopefully they'd been trained right and are oriented to some of the equipment/procedures we favor. I pay special attention to OW students and look at them as our future core.
Dive travel. I've taken a break from this for the last year, but annual trips to tropical locations can be a good draw and contributes to the cohesion of your core group. If you are too busy, you can send a DM on a free trip if you have enough folks. I'm sure you've cultivated contacts with dive ops in resort regions...