The first place to look is on the base of the piece for some kind of brand name or authentication, but also the general rules of the weight of the piece, often lead crystal pieces are heavier, also the amount of cutting that's on the piece adds a great deal of value and again the refraction of the light, the more color you can see through a piece of crystal are clear, piece of cut crystal, you are basically seeing that lead content and ensuring that its a real crystal piece. There are several stores, antique stores that will stock heavily in crystal items and they may be a good resource for collectors. Another great source for that kind of information would be various publications. If a search is done online for books on glass or crystal production, there are lot of publications out there that have basically catalogued a lot of shapes and the styles from different manufactures.
