Random ideas in no particular order...
Learn which record labels and time periods TEND to be good and which ones don't. Generic examples:
RCA before 1965 = good or great
RCA after 1970 = doubtful
Mercury Living Presence = great or good, best records I own
Telefunken, Erato, Harmonia Mundi, London ffrr, Archiv Production all tend to be good/great.
Westminster = gorgeous mids & clarity, maybe rolled off HFs
Monitor Ebay and Audiogon auctions prices (not seller classified ads, which may be inflated). People normally pay more for what they know is worth having. Don't bid at first, just watch - that way I can get the good ones I still need! :)
Look at what the audiophile reissue houses like Classic Records and Speaker's Corner have chosen to re-release. They choose individual recordings they think will sell, presumably based on artists, program and performance, but also based on sonics. They don't always get it right but they usually do, since they get to listen to the master tape before deciding.
Check out Arthur Salvatore's list of desirable recordings at www.high-endaudio.com. I've only heard a few of them but he's never steered me wrong. Nothing that makes his lists is going to sound less than great.