Along with tales of fabulous finds (cashmere and more)I detected a bit of anxiety amongst the commenters: can you really find great stuff at thrift stores?
My answer: it depends where you live. I myself have thrifted in various places. Right now, I live in a small town with a tiny affluent population, a mid-sized middle class, and a large very poor population. Surprisingly nice things show up on occasion and the prices are very low. There is little competition for the things I look for.
I once lived in a small town with a small college. The town had been decimated by unemployment. I dutifully wandered over to the Salvation Army once a week for a year and found perhaps two items. That may be stretching it.
When we visit relatives in affluent Northern California, I have seen great things, usually clutched by others. There are lines of what look like bonafide hippies circa 1971 lined up outside a tiny thrift shop in Marin. When it opens, they rush in; within minutes, the stock is decimated.
So--to oversimplify--what you find depends on the population and the competition. There are zillions of other people shopping, many with more expertise than you possess. A large proportion of the shoppers are shopping for a living. They know what they are doing. Many go every day. One of my thrift friends is an expert in jewelry: she laments the fact that she can no longer find Danish silver to sell on Ebay.
If you try a few times and find mostly ugly overpriced stuff...well, that is the way it is most places. I am lucky because I buy things for my whole family: my chances of success are higher than if I were shopping for just me. And I'm mostly looking for quotidien stuff: a colander for Frugal Son, some books to read, etc.
Recently, I have discovered the joys of on-line second hand: not terribly cheap, but reasonable. My favorite so far is Poshmark. Check it out. (Since I wrote this I've noted that some of the on-line resale sites have really raised their prices. On Poshmark and Tradesy, the seller sets the price. Twice Clothing, in particular, seems to have really jacked up its prices).
In the more than 30 years I've been thrifting, I've found a vintage Gucci bag, a pair of Chanel loafers, and a single Hermes scarf. That's one status item every ten years. My best find this year: a set of Sferra sheets (no cases).
Shopping in bad thrift stores is time-consuming and depressing. If the pickings are always slim, it's not you.