For me, it's like when you taste wet cardboard or a wet dog.
You look for great vintages. Great vintages can carry inferior producers sometimes, so a great year, like 2005 Bordeaux, 2005 Burgundy, 2004 Brunello, '97 and 2001 in California Cabernet. A great year can really carry weight. So vintage would be the first way. If I see a great year, under 10 bucks, it's got a better chance. It's got a shot.
After that, producer. Legacy of producer. Who's the guy or the gal making it? Have they made great wine in the past? I'm going to trust a producer like Nicolas Joly or Chapoutier, one that I've liked in the past, even though I haven't had this new vintage. And maybe even if I've heard the vintage is inferior, great producers make great wine in inferior vintages.
So there's a lot of interesting opportunities within wine to find deals like that.