Familiarize yourself with the different types of art. Animation art consists of original production cels, original production drawings, conceptual art, hand-painted limited editions and sericels. Original cels and drawings are used to make cartoons and represent one frame or movement of a character. Concept art is also original, but it is pre-production and not actually photographed for the film. Finally, limited editions, or sericels, are recreations of famous scenes. These are released by the studios and often numbered with certificates.
Establish a budget, then research prices. If you are a fan of Snow White, for example, you should know that artwork runs between $200 for a sericel, up to thousands of dollars for a production cel on a background. Take time shopping around. Ebay is a good resource, or if you are buying original art, check with specialized online galleries such as The Animation Celection (see Resources). They might not have the exact piece you see online, but they can give you information on comparable pieces and prices.
Buy from a reputable source. No matter who you buy from, always ask questions. Key questions include: "How long have you been in business?", "Does this come with a certificate of authenticity?" and "Where did you get this?" A safe gallery to buy from is The Animation Celection (see Resources), which has been in business for 20 years and offers a lifetime guarantee with its certificate of authenticity (COA). If you're going to purchase through an auction, Christie's (see Resources) in New York is one of the oldest and best-known auction houses.
Shop around. Go online and find as many sources as you can. Search "animation art," and you will find a good selection of specialized galleries and auction houses.