1)
No matter how much you think you know or how much you actually do know, there's plenty more to learn. In short: stay curious.

2)
Become a liner note junkie. Pore through all liner notes, especially for details on musicians, producers, labels, etc. You cannot remember everything, but enough will stick which may enable you to recognize something about another CD that is important.

3)
Look through ebay completed listings. Go to 'advanced search' and look at high-priced finishes, or a particular title or artist, etc. Not only will you see what is and isn't selling, but you will notice small differences in various pressings and you will also notice little mistakes that a seller makes that may have cost him.

4)
When at any retail store that sells new, sealed, and low-cost CDs from a budget label, study the names of those labels. Most are pretty crummy and cheesy, i.e.: not original recordings, poor masters & sound quality, etc. That way, when you are hunting in used CD bins, you can better differentiate between cheap budget product, good imports, and good domestics.

5)
When browsing used CDs in stores that display them spine out, run your hand along the edges (which is actually the top and bottom of the jewelcase) as you browse. Most jewelcases are ridged, but during the first few years they were smooth & frosted. When you feel a smooth one, take a closer look, you may have a nice early Japan or West Germany pressing, or some other valuable early pressing.

6)
When looking at CDs for scratches, try looking under an incandescent light bulb. A natural or fluorescent light may not show light scratches that do appear visible under an incandescent bulb.

7)
Watch out for record club/music club issues. Yes, they essentially are the same as standard releases, but collectors - for good or ill - generally don't want 'em, so if you are planning to resell check CDs and inserts carefully.

8)
For import pressings (from a U.S. standpoint), concentrate particularly on Japan pressings, they are often considered superior to others and are highly collected (they aren't always, but you get the drift). Also West Germany/Germany, U.K., Canada, Australia, Sweden, France, to name a few. Be wary of Italy, non-Japan Asian, Russia - a lot of 'grey area' or outright pirated pressings so tread lightly.

9)
When selling, give the catalog number (cat#) of the CD, it typically appears on both the CD and spine part of the back insert and may include some letters in front of the numbers. This is more important than the UPC barcode number (which often has the cat# incorporated in it but not always).

10)
Check out any place that might have used CDs: record store, book store, thrift store, garage sale, flea market, estate sale, internet/ebay - you can strike gold at any of these locations (you'd be surprised).

If you have found this guide to be informative and helpful, don't forget to vote 'yes' below and....Happy Hunting!