I usually read reviews by some people that i trust. The guy that started the topic usually posts reasonable reviews and i usually pay attention to his thoughts. Than i download several releases that i marked and hear them. If i like it i might buy it. I usually prefer artist albums and preferrably local, Israeli, releases, although they are quite sporadic nowadays... If it's a new and small label than i usually prioritze it's purchase. If it's Spun/Hommega/BNE i usually think twice. I seldomly buy mainstream. Only the worthiest pieces like Pink Floyd or anything in the caliber.
My 3 cents.