Have some super display tanks: Planted, African, and Reef, at least. You can inspire awe and encourage MTS. For example, I never wanted to do SW until I saw my LFS's invert reef tank. I came back a month later and spent $1000 to get one of my own. And you can see how many people here get hooked on the planted tanks after seeing nicely done aquascapes.
I'd like to see my LFS carry a variety of less common fish. The one I go to carries a whole lot of pretty typical beginner fish. But many beginners start out at PetsMart or other chain stores, and can get their stuff more cheaply there than they can at a private store. I've been keeping fish for over 10 years, and I've kept everything PetsMart could possibly offer me. I want things I can't find at a chain store. What's more, I'm willing to pay quite a bit for something nobody else has, so LFS, you should indulge me.
Also, you should host an aquarium club meeting or two. Not only will they be mentally browsing around during the meeting and itching to buy something afterwards, but it's also a great way to let serious hobbyists know there is an equally serious LFS around.
I second everything 7Enigma said too. Brilliant.