I would say the closet guideline is the Greysheet/Bluesheet series of publications. The top graded coins will always bring the best money. I don't mean the Pop 1 or 2 coins, I mean in each grade. i.e.; a super nice high end XF original, no damage, no cleaning, no problems will always bring more than a low end problem XF coin, and usually way above ASK pricing. So buy the best coin you can afford, I learned there is usually another coin out there, don't jump too quick on the first one you find, study the series you are collecting well, get to know the striking characteristics for each year and MM, become an expert, you'll know when you run across one, and you'll buy smart. Collectors and dealers will aways want superior material in any grade or series and end up paying for it when the find it.
"Buy the Book Before You Buy the Coin" - Aaron R. Feldman - "And read it" - Me 2013!
ANA Life Member #3288 in good standing since 1981, ANS, Early American Coppers Member (EAC), Colonial Coin Collectors Club member (C4), Conder Token Collector Club member (CTCC), Civil War Token Society (CWTS) member, Liberty Seated Collectors Club (LSCC) & Numismatic Bibliomania Society member (NBS), USMex, Member in good standing, 2¢ variety collector.
See my want page:
http://goccf.com/t/140440