Grading Used Lps: What to look for?

Hey folks...my used options in my area include stores that use a fair,good, and fine grading system for Lps...however... since grading is highly subjective...there seems to be grave inconsistencies...I often find LPs with minor hair-line scratches cleaner sounding than mint Lps with some surface particles(even after cleaning)...any suggestions? For high demand used artists...stones,floyd,etc...the grading system is pretty forgiving and the price not surprisingly inflated...sometimes you really dont know how an Lp will sound still you bring it home...is this just par for the course for going used? ALso have Santana Abraxas which is warped and nicked...but is quiet as a church mouse...