This past Saturday, I did some earnest yard-saling. Here was the haul for the day:
11 long-sleeved school shirts
2 short-sleeve shirts
6 pair school pants
1 school shorts
2 play t-shirts
1 school sweat shirt
1 pair sneakers
a peg-board game (x-mas gift)
a shoe-box containing 19 bottles of fabric paint
a CD display case
a round tablecloth
I spent just under $18, and about 2 hours. If I had bought this in a thrift shop, I would have spent a bit less time, but a lot more money (I'm estimating, a bit more than $100. That's a difference of something like $80 for one extra hour of shopping!)
You'll notice that this list is heavily weighted toward kids' clothes. Going yard-saling has the best pay-off for people with children, I think. My boys are very hard on their clothes, so I've learned to get extra outfits I can pull out mid-year when their current shirts or pants are no longer decently patchable.
Yard sales are also good ways to furnish a house or apartment that doesn't have much in it yet. But if you're shopping for something specific (like a round tablecloth), you might spend just as much time looking around at yard sales before you can find one you like -- a thrift shop begins to make more sense. For that reason, my friends and I swap lists of things we're looking for. (The CD case and tablecloth are examples of things I bought for friends).