Whoever talked about a clean bathroom, I agree. My favorite FLGS for transfers has a filthy bathroom. That is the only problem with the store.
Seconded. A dirty bathroom with insects, the stenches of ammonia, tobacco, and axe, and graffiti just screams 'redneck heap of scrap'.
If you will have dogs in the store, get low allergy dogs as some customers may be allergic and you don't want to scare them off.
Some people are Cynophobes, or have phobia of dogs. I'm one of those people whom dogs seem to hate. Frequent barkers, growlers, and otherwise loud, underfoot, and in your face are things to avoid.
No Smoking. The best store for gunsmithing in my area will get caught sooner or latter for violating state law. I don't want to walk out of a store smelling like cigar smoke.
This can be particularly important for the female clientele. Women, especially my mother, have supernaturally good senses of smell and find the most random things repulsive. Cigarette smoke is often one of those things. And whatever happens, don't allow in any Marijuana smoke. Thanks to my roommate, I now start coughing when I just smell the odor of the plant.
Don't have a coffee table, locate above a cafe or as a secondary business next door.
In stores, the coffee table always turns into an excuse to sit for a while and enjoy the free drinks without buying anything.
Have more capital than you think you will need.
Axiom of a college student: Everything costs more than it does.
I agree on having cheap ammo for sale. Also stock more unusual cartridges like non-corrosive 7.62x54r (even if its just a box or two)
Cheap ammo and rare cartridges are the things that separate out good vendors from the rest.
Leave politics out. You don't know who will walk though the door and I know quite a few non-traditional gun owners. On the same note, don't say dumb things about gun bans that I know is not true.
Politics is the fastest way to get into an intractable fight with someone. Leave out the signs and adverts saying things like "Real Americans", "Patriots", or "Liberals not welcome". It makes your store and everything associated with it look like backtwards bigots. A large proportion of the gun public and the prospective gun buyers are not politically inclined, and could very well be wildly opposed to your rhetoric. Include religion on the things to avoid list. Islam and Atheism are the systems that cause the hottest arguments. Judaism isn't quite so sensitive, but with the perseverance of Jewish Conspiracy Theories and antisemitism and the memory of the Holocaust, it's still a slippery slope. Finally, if I hear or see one more person, salesman, merchant, or store troll about a gun, ammo, or anything ban, I'm going to compare the hardness of the nearest wall and my head.
Have an email list and send out unadvertised specials to customers.
Specials are great ways to motivate people to buy now. As I learned in Vector, everybody loves free stuff.
Get involved in the community. There is a nearby pet store that has a tradition of local politicians visiting it and getting a picture with the parrot. Try to get to the same point.
Hey, if you're lucky, your Picture with Stag Arms Santa photo event will get picked up by the media.
Here's a fun game: take an uneducated neophyte to a gun show. Go up to the table of some Joes selling revolvers, pistols, rifles, shotguns, EBR's, and other random guns and have him ask the following questions: "What do you recommend for Home Defense? Why not that other gun for Home Defense? Can I open carry that pistol? Which of these is best for SHTF? What if Obama tries to ban this? Which gun should I get for my Mom?" Have him give you the answers he receives. Then give him a numbered list of all the misinformation he received coupled with the truth.
Do have a knowledgeable, pleasant staff. I am willing to pay slightly more for it.
A good staff makes or breaks a business based on direct sales and interaction with the customer.