Identify the manufacturer's mark, usually found on the bottom of the pottery piece. Manufacturers sometimes imprint or paint with glaze an identifying mark to distinguish their pottery from the one made by their competitors. Among the earliest and most famous trademarks is the double sword used by the Meissen manufactory. Marks can be found in various sources either online or at your local library.
Make note of the texture of the glaze. Does the glaze look smooth, crackled, or crystalline? Salt glazing results in a hard, glassy surface with the texture of an orange peel. The thick "fat lava" glaze of the 1960s and 1970s often has a lava-like cratered surface. However, lava glazes can also result in crystalline surfaces, more like cracking ice than lava.
Make note of the color of the glaze. Are glazes applied as painted decoration, or as stripes of color? Salt-glazed stoneware is often decorated with painted designs in cobalt blue glaze, one of the only glazes that can be fired at the high temperature required for salt-glazed pottery. West German pottery of the 1960s to 1970s is often glazed in eye-popping colors.
Make note of the shape of the pottery piece. An explosion of creativity in German pottery after World War II resulted in exaggerated and asymmetrical shapes, some of which are distinctive to certain manufacturers. For example, the pottery manufacturer Ruscha introduced "Shape 313" designed by Kurt Tschörner in 1954. His distinctive shape remained popular until the factory closed in the 1970s.
Gather your observations and begin researching online and in the library to find similar pottery pieces. Collectors' guides, exhibition catalogs, and collectors' websites are useful tools to find matching marks and similar shapes and glazes.
There are several collectors' guides online, such as ginforsodditiques.com (West German Pottery) and www.mihummel.com/reference.asp (Hummel figurines). Some companies, like Meissen Manufaktur, store images of past trademarks on their website (http://friedrich.meissen.com/index.php?id=159&lang=1)