I tend to think shops should focus on the basics. Gas fills, gear service, equipment sales and training. The emphasis should be on enabling the customers to acquire all four with as little hassle as possible.
I consider these basic expectations:
1) Gas fills. I should be able to walk into any dive shop and obtain an air fill while I wait, and some variant of 30-36% at most shops. I should be able to rent a variety of cylinders common to local diving, or have my own cylinders filled. I should expect to find evidence of recent gas testing, the fill station should be clean and well maintained, and pricing should be posted in a clear and conspicuous manner. Cylinders should be filled to rated pressure, or otherwise explained and charged appropriately. Blended gasses should be within 1-2% of requested mix. I understand the need for lead time for technical gasses or custom blends, but keep it within 48 hours. If technical diving is popular in the area, a shop catering to technical divers should have those gasses banked and double/deco cylinders available for rent.
2) Gear service. I should be able to walk into a dive shop and have them service the equipment that I purchased from them, or that they are a dealer for. If they can't do it in house or don't sell/service that brand, they should offer options for having another shop handle it. Their techs should be well trained and experienced, with manufacturer training workshops a bare minimum. Service should be completed in a timely manner and turnaround expectations should be clear. Pricing and the scope of work to be performed should be clear. Documentation should be provided of all work performed, with test results listed where applicable. Recommendations and advice should be based on facts and evidence, not derived from common industry scare tactics.
3) Gear and Training. A selection of gear and training options is nice, and I'd prefer shop place their energy in making sure that what is on offer in both regards is appropriate for local diving. Shops should, at the very least, have common replacement parts and wear items for typical local dive equipment. Shops should have a selection of rental gear that is appropriate for local diving. I should be able to equip an average sized diver for local diving using items in-stock at your shop; purchase and rental. A new diver should be able to learn to comfortably and capably explore local dive sites, using the training available at a local shop. A diver should, after completing OW, AOW and Rescue, have the confidence to explore a wide variety of local dive sites, independently of a shop organized dive or divemaster, with a similarly trained buddy. Opportunities for continued education should be provided at all levels of diving.
Community building and activities are nice, but that always seems to be more for the promoting the dive shop's interests and engaging new and inactive divers. Dive shops should focus firstly on promoting diving. At a minimum, that means they should offer advice on local dive sites and dive opportunities, and maintain a network of guides available for hire, or local divers interested in diving with new buddies. They should know the schedules, rates and contact information of local dive boats and provide this information. They should be out diving for fun.
I can list numerous examples of failures for all the above, in shops across North America, but I tend to think the people paying attention to this thread understand exactly what I'm talking about.
Bottom line: too many have ignored the basics and become little more than a travel agency with a scuba themed gift shop.