Do not buy on impulse! Make sure that you thoroughly research any artwork you have an interest in buying. Catalogues raisonnés are very useful in conducting research on the authenticity of a given work. IFAR's bibliographic databases on published catalogues raisonnés and those in preparation will indicate the artists for whom catalogues exist. Relevant catalogues should contain information on works that, at the time of publication of the catalogue, the catalogue authors considered "authentic." If there is no catalogue raisonné on your artist, research can be pursued at libraries and other research institutions. Museum libraries can be helpful, and many public libraries have sections devoted to art. The Frick Art Reference Library in New York has an extensive photographic archive on individual artists, as well as access to subscriber-based Websites and digital resources relevant to collecting and issues of authenticity. If still in doubt, consult an expert in the field.
(Source: Intl Foundation for Art Research)