Back in the 70s you often bought blind going by artist, label & writer/producer, of the latter Holland Dozier, Van Mcoy etc. were all bankers, nowadays with the internet and all you can usually vet a track before you buy it, this can take some of the excitement from opening the package that arrives through the door but its maybe not a bad thing to buy what you like.
I can remember setting the record player next to the phone to play some of my latest arrivals to my mate Kev and he did the same for me.
Collection wise lately I've concentrated on collecting UK reissues of top northern sounds from the 70s lables like Brunswick: Adams Apples, Gene Chandler Artistics, ABC : Willie Hutch, Reflections & Sapphires London: Yvonne Baker etc. UK, Pye, Contempo, UA, Capitol all reissued (legally) some of the big tunes of the day I've about 300 titles now and they've not cost me a kings ransome. The good thing with these is they may be more readily available out of junk shops car boots.
Good Luck