I've had a bit of luck with local stores although my favorite recently closed down thanks to a GameStop cropping up across the street. Thankfully, a new game store has taken their place in another area which is quickly gaining favor with me. Still, any retail store only has so much. If you want something really rare or imported usually you're relegated to search around on eBay, Game Gavel or specialty forums.
As of late I've been checking out various online ways to buy, sell, and trade games. There's certainly not a lack of websites devoted to this. I looked into Goozex, Gylde, SwitchGames, and a handful of other sites and found them all interesting little ventures. Goozex has by far the largest amount of users currently but before that it seemed the best option was GameTZ.
What I've come to find while checking out these various sites I've noticed that most are severely lacking in having a simple to use website. Glyde comes very close to this but the simplicity is in fact a little too much so and there aren't as many items available. Goozex is a super cluttered website and feels like it's full of teenagers. There isn't necessarily a thing wrong with that but I wouldn't really trust a bunch of kids who are going to goof off to give me a game in good condition, ship properly, etc. I know there are some fine folks using the site, but there doesn't seem to be a way to tell who is very reputable. Also, while they have a "retro" game section now (they didn't always) there's still tons of consoles missing and apparently many users don't even check their carts prior to selling.
GameTZ is ugly as sin but you know what, it doesn't need to be gorgeous. I had to look around a while to get acclimated to the layout of the site but it has quickly become my favorite site out of my searches. Almost every game from the NTSC region is listed, and many popular Japanese ones are as well for various consoles. I've seen reputable users offering up games that I desperately want and with 500 transactions under their belt, I'm very ready to trust them. The whole site is based around bargaining too, so you can work your way to a better deal, if you so desire.
I'm thinking that this is going to be the site I use in the future for buying, selling, and maybe trading too. Well, first I'd like to pawn off the stack of horrible Asteroids and E.T. carts I have at a yard sale or something, but then become invested in the site. I really like it and think it's worth checking out if you want yet another alternative to all the online shopping sites out there and maybe wanna get rid of a few things.
I'm curious what other websites, stores, forums, or whatever that gamers use. I'll keep searching because GameTZ apparently has been huge for at least 10 years and I only found out about it sometime last year. I've known of Goozex since its inception but just have never had enough trust for the site.