What should I look for when purchasing a quality album?

I think the first step is to identify the piece of music you want to acquire, and if it's classical figure out which recording is the one you want (that's a musical issue, not an audiophile one). If not classical, there may only be one original release, or there may be re-releases (usually in better shape but sometimes not such a good pressing).

I have mostly had good luck with used records, and if from discogs I sort the available disks by condition and look for the best one I can afford. If you are in a used record shop you can see for yourself if there are scratches. Everything gets cleaned before it goes near one of my styli.

Buy what you like to hear. Do buy used LPs but only under the following stipulations: (1) you examine the LP yourself, both sides, and there are no, zero, scratches or blemishes, and the surface retains its new vinyl sheen, or (2) you buy from a reputable source on line that grades their used LPs, and you buy only Grade A, or (3) you’ve grown to trust a vinyl reseller and he offers right of return if the LP is unlistenable. You almost have to be willing to buy used LPs if you want to accumulate a decently large collection, and if you are starting from scratch, unless you are wealthy and/or careless about the amount you spend.

There are dependable quality labels, but any attempt to list those will inevitably be incomplete. In jazz, I can recommend in no particular order ECM, Steeplechase, Pablo, Verve, Columbia, some Capitol, Vanguard, Pacific Jazz (old label, mostly mono), Riverside, Contemporary, Atlantic (somewhat colored but will produced), Blue Note (to me also somewhat colored but very collectible and therefore sometimes ridiculously pricey), Jasmine (which seems to be reissues but good sound), MCA,..... I’ll stop there. Someone will recommend Direct to Disc labels. Yes, great SQ but the artists on those labels are seldom first rate.

I use Music Direct if want a new album. Typically buying only audiophile pressings. I have had very bad luck with Amazon. 

If I want used, I go to a local store so I can examine the record carefully.