Second hand shopping can save you money when you only pay a fraction of the cost of an item. Some sales only have junk or overpriced items. How can you be sure you are getting the best deals for your money?
Plot your course, don't waste gas driving around - Get your newspaper listings or check the online listings in your area and grab a map so you can strategically plan your course. You can pin point where you think the good sales are and determine which to go to first then move from one to the next.
Learn where the good spots are - some areas just seem better than others for sales. Ask around and see if others you know have experience in where to find the good stuff and which places to skip.
Know your prices- Get familiar with the brands, prices and quality of things you like and need. If you know what the stores around you are charging for items, you are less likely to be taken in by a bad deal.
Don't buy what you don't really want or need - Just because it's a dollar and maybe someone could use it doesn't mean you should buy it. Know what things you really need and want just like when you grocery shop with a list. Impulse buys are easy to do when you see so many things at such low prices. Save yourself money and don't buy on impulse.
Bring supplies! - Bring bottles of water or other drinks, snacks and handy wipes or wet cloths so you don't have to stop for refreshments or to clean your hands.
Read what the Dollar Stretcher has on yard sales...
Yard Sale Etiquette
Yard sale Christmas shopping
How to Avoid Yard Sale Junk
I posted about this topic just recently on my blog (http://ecofrugality.blogspot.com/2014/06/the-three-types-of-yard-sales.html). The gist of it is that there are three basic types of yard sales. The first is the Clearout Sale: someone just looking to get rid of unwanted stuff, not to make as much money as possible. At these sales everything is priced to sell, but a lot of it is junk. You have to visit a lot of these to find the good stuff.
The second type is the Revenue Sale: the seller's main goal is to make money. You may find higher-quality goods, like antiques or designer clothes, but the prices will be a lot higher--often close to the amount you'd pay in a store. If you're looking for something specific, you might find it here and save a little money, but you won't find any real steals.
The third type is the Reliquidation Sale. Basically, someone has bought up a bunch of junk at rock-bottom price and is now trying to sell it for a profit. You can always spot these sales because there are 100 identical items on a table: copies of the same book or album, cheap plastic toys, samples of cosmetics and shampoo. Even if there is something you might want, it will be priced higher than in a store, because the seller is trying to make money. Don't even bother looking.
Clearout Sales are the best for finding bargains, but you need to hit a lot of them, so the best possible strategy is to go someplace where there are a lot of sales concentrated in a small area. Town-wide yard sales are the best for this. A week ago the town where I grew up held its annual town-wide sale, and we found a power sander, a case for my ukulele, a couple of gifts for nieces and nephews, two screwdrivers, a package of Dremel bits, and a small decorative tin, all for around $11. Of course, we also spent $2 on cookies and lemonade from enterprising youngsters, but I consider that a reasonable purchase.
Good tips here, Haverwench. When I was hitting yard sales routinely, I quickly learned which ones were money making. They had yard sales every month; they were going around and buying things up at other sales to resell them. The prices were higher there and often it was the same stuff that had not sold the sale before.