I'm not a big yard sale person, although a few of my biggest scores were at garage sales. My main problem with them is you have to hit up 50+ garage sales to find a good deal sometimes, and if the sale is advertised with games it then becomes a race of who gets there the earliest and can get pretty dicey from my experience.
My best advise is to go to community garage sales where a lot of people in a relatively small area are having garage sales so you don't have to go far between sales. Obviously see what they have out, but even if they don't have anything always ask the seller and see if they have any video games for sale. I can't stress how important doing this is. A lot of time saying this will jog their memory or they'll decide to sell games they may have been unsure about selling, but since someone is asking they're more inclined to let go of them. Another advantage of asking even if you don't see anything is they are caught off guard and don't have time to research what the games are worth, meaning you have a much better chance of getting a good deal on whatever they're selling.
Despite how effective doing this is when people actually have games, actually finding someone who has games for sale is tough. As I said, I've literally hit up dozens of sales in a day and came up completely empty handed. It became so barren that I eventually lost the motivation to even go out to sales anymore. One strategy that I've thought of is hitting up sales in older, more established neighborhoods since there's a greater chance that people have lived there a long time and possibly still have old games that belonged to their kids or grandkids. I've noticed in newer neighborhoods people typically got rid of this stuff before they moved because they didn't want to worry about moving it when they moved into their current home.
Hopefully some of this helps.
