Dresden porcelain is a general term for the wares of a group of small factories working in the German city of Dresden from the early 1800s until the Allied bombing raids of World War II. Their wares imitated the products of the Imperial porcelain factory located in the nearby city of Meissen. Most later pieces can be clearly identified as Dresden porcelain because of a backstamp, but many early pieces went unmarked. This means that not all Dresden porcelain can be identified with absolute certainty -- dealers often describe such pieces as Continental porcelain.
Look for the Dresden backstamp: A crown with a "D" under it, or the word "Dresden," usually printed in blue or green ink. This backstamp was shared among a number of different factories, but didn't become common until the 1880s. The addition of the word "Germany" indicates a 20th century piece.
Examine the piece for the presence of lacework. Made by dipping real lace in porcelain, this was used to decorate the skirts and cuffs of figurines and the borders of plates. This is a strong identifying feature of Dresden porcelain as the technique was widely employed on its wares.
Scrutinise the porcelain itself. This should be very pale and glossy, elegantly potted but not eggshell thin.
Look for signs of hand decoration, especially hand-applied gilding and painted floral vignettes. All Dresden porcelain would have been hand decorated. Identify hand-painted decoration by looking for unevenness in the thickness of the paint and an absence of printed outlines around the edges of the design.
Consider the style of the piece. Dresden produced a range of wares from plates and vases to figurines, but they all display the same Rococo influence. The effect is fussy, pretty, delicate and feminine, with moulded or painted decoration involving flowers, shells and scrolls and background colours of vivid pink and blue.
If your piece matches these characteristics, then it is a sensible assumption that it is a piece of Dresden porcelain, although it can't be proven without a backstamp.