I have been an avid thrift/consignment store shopper for years. Getting a really good deal on a pair of Levi's somehow makes me happy, and if I get them used they are already broken in. We have several charity run and independent thrift stores in our town. I try to go to the charity run ones as I don't have money to give out of pocket to charity, but at least this way I can help some.
Some tips I have learned in shopping over the years:
1- The thrift stores in the richer areas of town generally have better quality stuff. If you really need something to last start there first.
2-Look at what the garment is made of. Denim and heavier cottons hold up well, and are less likely to fall apart on you than a used rayon or polyester.
3-Children's clothes are usually the best deals, as kids generally outgrow their clothes before they are worn out.
4- Try things on if you can, you don't know if they have shrunk in some one else's dryer.
5- If you decide to buy toys, look over it carefully for safety. Also check for all the parts. Generally you can't return it if it is missing something.
6-Don't buy used cribs or car seats this is just too risky. You can't tell if a car seat has been in a wreck, and if it has it may not be strong enough to protect your child in one.
7-Check your shops frequently, the merchandise changes often because of donations.
8-If you are buying furniture, carefully inspect it. Makes sure there are no hidden tears of stains that you aren't willing to live with.
9-Know what something costs new. Some consignment sales allow people to price their own clothes, and items can be priced high for used items.
10-If you are buying anything that plugs in, check to make sure it works. There should be a place for you to test it. If you are buying an appliance, buy from somewhere that does their own appliance testing. I know Habitat for Humanity Restore does this before allowing some appliances to be sold.
Good luck finding deals!