Just like in engineering, I quickly learned in picking that there was no way I could remember all the particulars about the millions of items out their or their value. However, I found several resources I could go to for answers. Some of those are in book form, some on the internet, and others through word of mouth and experience.
Early in my picking “career”, I tended to lean more towards glass. The funny thing is that when I started out, I swore I would stay away from glass. There are just too many makers, types of glass, colors, patterns, and on and on. And a lot of reproductions (repros). However, after seeing tons of glass at auctions, I figured the supply was in my favor. Being from West Virginia, the glass capitol of the world at one point, there is a lot of glass available in the local market. Even though the laws of supply and demand are diminished in this global internet market, I knew there was a great supply I could tap. So I bought some glass price guides. I have a depression glass book, one on Fenton Glass, one on Blenko glass, a pattern glass book, a couple of carnival glass books, a book on glass lamps of the 180 and several others. I also have found some great websites for determining glass patterns, colors, etc. The daunting task of figuring out a piece of glass was becoming less daunting. There is still a TON of stuff that I don't know, but I'm gaining a better of understanding of where to look to find out.
One place that some may not consider as a resource for information is Facebook. You would be surprised how many Facebook Groups exist for all kinds of collectors. There is a Facebook Group for carnival glass, Fenton glass, depression glass and many others. And that is just some of the glass pages. There are pages for knife collectors, camera enthusiasts, pottery aficionados, and just about anything else you can imagine. There may even be a collector's page for belly button lent. You'll have to look that one up. I'm not even going to look. The thing is, if you get a piece that you may not be sure about, you can post a picture on one of these pages and people seem quite eager to lend their knowledge.
Other free resources online are blogs (like this one), mailing lists, auction companies that list their “sold” prices, eBay's completed items searches, and websites specific to your particular interest. There are also some pay sites that provide great information. You can find price guides like Worthpoint, Invaluable (previously ArtFact), Kovels, FindArtInfo, and a lot of others. The thing is, even with the monthly fees, some of these resources can easily pay for themselves during the month when you can easily find the right information. For instance, lets say you go to a yard sale. They have a widget that is somewhat rare. They looked online but couldn't find any real information or prices. However, you take a quick look at Worthpoint on your smart phone, and voila, you know the widget is worth 83 rubles. Or whatever. Well, you get the idea.
While it may seem a bit overwhelming with all the potential resources, the key is knowing where to go for a particular item. And that knowledge is definitely power. As Ralph Waldo Emerson said, “Unless you try to do something beyond what you have already mastered, you will never grow.” So sit back, read some great price guides, peruse internet forums, and learn.