Britfag here. We don't really have as many games stores as you guys, but I'm fortunate in having a pretty awesome FLGS in my hometown.
The store's pretty big, and divided into two areas.
Front of house is the shop floor, with shelving and the register (between the product shelves and the door, with CCG packs behind glass) and a display table of the week's new releases or featured games. The shop floor is set up so that jigsaws, boardgames and other traditional games that won't scare the general public are up in front, being the first thing that customers see when they come in. The RPGs and wargames are towards the back, but still in line-of-sight of the register. The register's got counters on two sides, with a small alcove behind it where regulars can lurk and shoot the shit with the proprietor without getting in the way of customers who want to make a purchase.
Back of house there's a pretty big games room with a crapload of IKEA tables and chairs, where they run games nights in the evenings (boardgames, wargames) and CCG tournaments at weekends. No one's allowed out back when these events aren't running, and there's always a member of staff in there at such times. I think there's a smaller room for the D&D players as well.