Some of the things that I have seen work well in some of the gaming stores I have been to (and helped out at).
Build a loyal clientele base -the one big way I saw this happen was to have a 10% / 20% / 30% off members (we had cards and everything). This was done by having clients keep their reciepts and when they reached a certain benchmark number they turned in the reciepts and got the discount from then on. IIRC the benchmarks were pretty high too, at $100, $300, and $500 respectively. This also helped to woo people away from the online stores.
Post a schedule somewhere (big) as to what and when the new products are coming out....it helps to build anticipation for the product.
As said before a bullitin board is nice to have in the store.
One store I frequented sold new products (1 week old or less) with a big discount (25%) and then sold them at normal price. Said that it helped to generate large sales initially (away from the big chain stores like Borders).
Don't be afraid to leave out catalogs for the products that you don't choose to physically have on stock....that way your customers can order it in a week and get it, without you having to keep a very large inventory of stuff that will sit around on you.
Have a computer on hand for your employees (or you) to look up reviews, product release info, game design forums, etc. This way they will have the knowledge to talk to your customer base.
Keep your books in a very open and easily viewable place, in fact you may want some kind of help when you lay out your game store to make it easily visable from any point in the place. Shoplifting can eat up sales profits so quickly that it is scary and can send you packing quick. I talked to one Barnes & Nobles manager and she told me that during december alone they suffered about $50,000 in revenue loss from shoplifting. Know it yourself, and teach employees what to look for.
Versitility can be a valuable tool. Board games have been said before, and many are enjoyed by gamers and others alike (Risk, Settlers of Cataan, Axis & Allies, Rio Bravo Games, etc.) Also have small items (fake liscenses, credit cards, pencils, gag gifts, candy, posters, calanders, prop swords like LotR and lightsabers, whatever.) to help alleviate the slow product months. One other thing, comic books sell pretty well (at least monthly), and you can pick and choose with a few select books (KoDT, Noodwick, Dorktower, PS238, PvP, etc.)
As has been said in the past, Trading Cards and Colllectible Minitures! They sell well, and they come out often.....but don't end up getting 10 boxes of crap that won't move. Look around and see what kids are buying and stock that, just get it first and advertise on your window (we have Yugio or somesuch). One thing, some minitures are great to look at, but have such a vast collection that they are a real burden to stock (games workshop comes to mind, but there is others)....try keeping a catalog (with pics, maybe from the internet) for people to order from.
And perhaps the simplest advice is to have a reliable supplier who has a very large inventory and can get the items in a timely manner (especially on the release day...gawd knows you will loose sales when something comes out elsewhere and not at your store!!!)
I don't know if you have already chosen the location of your store, but when you look for a place if you can get a lot of foot traffic (movie theaters seem to be ideal as people are waiting for something and have money to spend) or by a supermarket (people drive by shopping and happen to see your store, etc.)
One last thing, out of curiosity just where are you locating your store? I ask because I live in Seattle (Federal Way actually) and would be interested in at least stopping by and checking the place out.
Good Luck
Xyth