1. Music forums. Generally not this one, as I have different tastes from most people on here. More like garagepunk.com or a handful of rockabilly, psychobilly, punk, etc forums.
2. My local record shop, the mighty Reckless Records. (Yes, I still buy music. How quaint!) If it's in the rockabilly/garage/surf section, there's a good chance it's good. Plus they let you preview before you buy, which helps in finding quality soul or jazz.
3. Band name. Silly, I know, but generally if a band name has "Thee" in it, it's good. See: Thee Headcoats, Thee Fine Lines, Thee Mighty Ceasars, and a million other great bands.
4. Label. If it's on Norton or Crypt, it will make it onto the list.
5. Friends. Either friends saying "hey, listen to this" or a friend saying "hey, my label released a new album, why didnt you buy it yet?" or something like that. Also, I will listen to whatever record finds its way into my mailbox. I don't know how they get my addy, but hey, free stuff.
6. Opening bands. Rare, but you luck out sometimes.
7. Compilations. 30 songs for 10 bucks? Sign me up. Usually can find a few good bands on one of those.