Do the discog research, if you're set on getting period presses to justify possibly spending more for a quality pressing.
Get ready to do some eye squinting to reference the deadwax. It's all in those often hard to decipher etchings to determine pedigree of a possibly overpriced used LP.
First run doesn't guarantee the best SQ, but generally may provide best chance of getting "closer to the master tape".
Greatest hits LP's are generally inferior in SQ compared to the same cut on the original album. I don't bother with them.
Easy way to immediately spot a reissue is a bar code on the jacket. If the original was released before 1980 or so, it usually wont have a bar code.