I'd llike to share a few things i've learned just by shopping Ebay and talking to the many helpful sellers.

• Ask about how the piece was polished. Some sellers will say this in their descriptions, but many do not. In the later Brilliant Period many manufactureres turned to a less costly method called Acid  Polishing.  This gives a sheen to the glass, but the crispness of the cut is lessened and it feels soft, not sharp. I consider this a kind of defect which should lower the price. (REVISION).. However, I have just read in the latest book by the Boggess's  that acid polishing was necessary for the more intricate cuts and that it is now considered more and more acceptable by experts when it was done correctly and followed with wood polishing on the larger surfaces. Poor acid polishing resulted in a watery look to the surfaces So it looks like we will need to educate ourselves on  recognizing the differences, which is hard to do from photographs. For Ebay buying this seems like a key question.
• What kind of blank was used? Blown blanks are more desirable because of the labor involved; they are usually older. Pressed blanks willl have a slight rise on the inside of a piece conforming to the outside pattern. Obviously you can't touch the EBay pieces, so be sure to ask.
• Become familiar with the differences among cut, intaglio and etched glass. In some cases this can affect the value, even if  the intaglio or etching is first-class.
• Know something about makers. There are some which produced only top-quality, such as Tuthill. Others had "good" and "less good" phases so you should try to identify the less good through marks or patterns. If you can't tell, be sure you love the piece.
• Know something about the "Flower Period". That's late ABP when manufactureres tried newer patterns including flowers (and sometimes other naturalistic patterns). Some of these sell for good prices and some do not. I haven't really figured out why, except if it's the manufacturer (again, Tuthill comes to mind). I think you have to look at some pieces in life and decide whether these are for you.
• If you don't know or understand something, ASK! I've found sellers to be most helpful and open in most cases. In one case the answer was "You tell me!"..guess whether i bid on that
• Look out for .vague descriptors such as "might be", "looks like", "a dealer told me" , "Grandma told me", "probably", etc. May or may not be the real thing, but if it isn't you have no recourse.
• Sellers will also educate you in general about APB glass if you tell them you are a beginner. I've even had them send me material to study.
• Be kind to sellers. Most do the best they can to be full and accurate in their descriptions. Some really are not familiar with ABP and could make honest mistakes; sometimes the descriptions can tell you that they don't really know what they are selling.I don't bid if the description is not full and detailed. Of course there are deceptive-by-design sellers, but i've met only two in three months and it was quickly settled when i mentioned Dispute Resolution and negative feedback.
• If you decide to become a serious collector, join the American Cut Glass Association.(They have a website). There is a wealth of information available
• Thank you for reading!
• COLD  WEATHER  NOTE (12-13-05) From another guide and also from a seller. If you receive glass from USPS or another carrier, be sure to let it sit unopened for a good length of time indoors before you open.  (sorry, can't get rid of italics)..If you bring glass from a cold environment suddenly into a warm one it may crack or shatter from the sudden temperature change.