In Washington, DC, the independent stores that hang on have a defined community. Kramerbooks at Dupont Circle has the young urban types mostly (I'm probably twice the age of at least a third of people I see in it). Politics and Prose has the settled folk of Chevy Chase and Forest Hills, with their children. Bridge Street Books on the edge of Georgetown--I don't get there often enough to judge, but would guess it to be nearer the Kramerbooks demographic, though the stock makes me wonder. (There are also used bookstores that seem to stay in business.)
So who is your audience? Have you the room to provide a place where people can gather to sip a coffee and use your WiFi, buy their NY Times from you, do the occasional impulse buy? I would emphasize this last. Of the last ten books I've bought, the majority have been unplanned purchases, something on a shelf (Kramerbooks, Second Story) or a table (a local church bazaar) that I didn't know I wanted till I saw it.