Let me start out with some things that deeply annoy me about LGS I've visited previously:
1. Politics: Having a plaque up on the wall reading "Salesman of the Year" with Obama's picture is funny and not really likely to annoy anyone. Having that same picture with crosshairs over it and "Public Enemy Number One" is a bit offensive to a LOT of people.
2. Foot-in-mouth disease. One shop I frequented in Alaska had a salesperson who was VERY VERY knowledgable, but RABIDLY anti-intellectual (as well as very very political.) He practically foams at the mouth talking about "Ivory tower intellectuals, and people with degrees." I hold an advanced degree. So does the friend I brought in to buy his first rifle. Guess where he's never coming back to.
3. Bigotry and Bias. I WILL show up in your shop wearing a t-shirt and shorts. That's just what I wear when I am not in my work clothes. There is a decent chance I showed up on my bicycle. You need to treat me the same as someone showing up in their fatigues. You really shouldn't judge people by appearance. You get mega-bonus points with me, however, if you can suggest a product that works with me biking.
4. Don't (expletive deleted) sweep me with the barrel of a gun. Even if the action is open. If you casually sweep me with the action open, You're going to do it at some point with the action closed.
What I look for in a gunstore:
1. A large and INTERESTING selection. Don't waste display space or inventory $$ on things that can be bought at every big-box store in the area. If 9mm glocks are massively represented in your area, why stock them? If someone wants ONLY a 9mm glock, send 'em to a big box store. Otherwise show them less common alternatives (XDs, cz75b, S&W M&P)
I love unusual firearms. Because of this, I pretty much want EVERYTHING KelTec makes that isn't a handgun. (And even some of their handguns. 30 round .22 winmag handgun? Yes pls!) If I can walk into your shop and take a look at an RFB, a KSG, and a Su16 in the same place, I'll be in hog-heaven.
Also try to come up with as many uses as possible for firearms, and try to have at least two options for every use. Hopping a plane to Alaska the next day? We have quite a good selection of "Alaska Safari" guns! Doing your first 3gun competition tomorrow? Here, this rem with an X-rail system and folding stock is excellent for the shotgun stage. . . What, your daughter needs a purse gun? Here, how does this LCP feel in her hand? How about this SCCY cpx2?
2. Whenever someone buys a firearm, offer to show them how to take it down. Even better, show them before they finalize the sale. Some people simply KNOW they'll lose a non-captive spring that is under high tension, and being forewarned is a good thing.
3. Offer alternatives, but not in a pushy manner. With the 9mm example above, I feel it is always good to show two alternatives that are equivalent. Point out the differences, and the similarities. This is especially useful for people that are nervous about the lack of traditional thumbsafeties on newer handguns.
4. If a common firearm frequently has a modification done, have both a normal and a modified version. Example: Glock 20 with a 20 or 23# wolff recoil spring. Or say a Saiga 12 shotgun with at least a nice muzzle break on it.
5. Have firearms for people of all body sizes. I dated a girl in Alaska who LOVED to go shooting with me, but had fairly tiny arms. She couldn't use any of my rifles comfortably until I put telescoping stocks on a couple.
6. Have "learner's kits" that include everything a beginner needs to get started. Package rates on Cleaning supplies, first 100 rounds of ammo, scope, and case would be nice. Remember, growing the shooting population should be the goal of every LGS.
7. Know what ranges in the area have rentals.
8. If your state allows hunting with a suppressor, For the love of Ghu, sell hunting rifles with threaded barrels. Even better, have at least one suppressed "package" rifle.
9. Offer a sighting in service. I've bought two handguns now that the windage was off straight from the factory. (A Tanfoglio Witness and an XD) I am not terribly comfortable fiddling with dovetail sights, and would prefer someone with more experience do it. Likewise putting in aftermarket sights.
10. Offer bulk ammo and Milsurp. I bought my Tokarev specifically because of the two boxes of milsurp at the store. Likewise if I see several spam cans of 7.62x54r next to a display of decent quality mosins, or even better SVDs and dragunovs, I WILL get one. . . (Or even better than that a 54r Vepr. . .)
11. No-name ammo brand for cheap? Yes please! Part of the reason I bought my 10mm was that a local store sold bulk Sheepdog fullhouse 10mm ammo.
12. Have bulk ammo in front of the counter, and small boxes behind the counter.
13. Nowhere in your store should it be so narrow that some random guy needs to rub his junk against me to get past me in an aisle. If your aisles can't accomodate two normally sized people without unwanted physical contact, get bigger aisles.
14. I like a ratio of 2/3rds new and interesting and 1/3rd used. I do not consider Milsurp weapons to be "used" I consider them to be Historic and Interesting. Having a couple interesting C&R firearms is also awesome. (I'm a nut for thompson m1928s. )
15. A wide array of reloading supplies is nice even though I personally lack the room to reload currently.