You could say that there is an upside to our culture's never-ending hunger for the new: the "old" ends up in thrift stores, where it may be found by conscious consumers with a little patience and effort.
About 99% of my wardrobe came from yard sales, thrift stores, and consignment shops. Nearly everything in my kitchen: plates, pots, and silverware, once belonged to someone else. Thrifting fits in with my ideals: it makes sense to reuse these perfectly good items rather than fit in with the throwaway culture that sloughed them off. The practice also fits my pocketbook (which was bought at a thrift store). Hand-blown wineglasses, designer threads and antiques all are within reach on the second-hand store shelf.
One of the drawbacks of thrifting is that it is also possible to buy too much just for the sake of a bargain. In the heat of the moment, in a crowded store with other thrifty hands reaching for the same item, I've been known to bring home something that didn't fit me (or didn't fit in my closet).
Here are some tips for shopping second hand
Thrift stores are like a dumping ground for misfit toys, whose slight flaws make them charming and unique. Fixer-uppers that require significant repairs before they are useful, however, probably will end up costing you more than the item is worth. On the other hand, some junk that is no longer good for its original use can be repurposed as art supplies or taken apart and put into do-it-yourself projects like reconstructed clothing made from t-shirts.
Shopping at thrift stores is a fun way to reduce your environmental impact, often by helping a charitable cause. Good luck, happy hunting, and remember that you don't always have to buy something to be a conscious consumer.