Antique and vintage fairs and flea markets are by far the best way to amass vintage clothing, accessories, furniture and other wares. My favorites are Alameda, Treasure Island and The Fashion Expo. I've gone to other antique fairs with moderate success, and I've attended music festivals that have vendors but most items are overpriced, cheaply made reproduced clothing. I used to buy vintage clothing through ebay but after awhile, the prices started to increase due to multiple bidding and often the items were not as described. Forget storefronts. Unless you know the employees, there is no negotiating the price.
The only downside to these fairs is the timing. They occur once a month, and the Expo is twice a year. What's a vintage loving shopaholic to do? Estate sales. They happen every weekend, anywhere and everywhere. So during the lull between Alameda and Treasure Island, I research the next estate sales around the bay. It's not so much finding them, but really looking into what's available. There are several aspect of vintage. You have to consider the culture, the era, the design of its time, etc. Keywords I look for are: Americana, mid-century, art deco, Edwardian, classic.
It's definitely a hit or miss. Most of the time I walk away empty handed, but when it's a good day, the effort is well worth it. I've bought a few dresses, some furniture and 78s for my victrola. The biggest purchase was my 1940s Wedgewood stove. It's currently stored at my parents' house, but when I buy my house, it will be the focal point of my kitchen. The prices tend to be dirt cheap. I pay an average $10. Of course the stove was pricey at $500, but it was very reasonable considering a stove in poor condition is at least $1200.
Not everything I purchase is true vintage, either. My latest buy was a few CDs that are Big Band compilations; more music to add to my library since I moonlight as a DJ. I also found a couple of DVDs that were set in the early 20th century. Aside from the entertainment value, I study the hair and makeup, the wardrobe and dialect.
I can admit that my love for vintage is a bit of an extreme, but I never really considered it a hobby as it is a lifestyle for me. Plus, there's nothing wrong with bringing back class.