When looking to add artwork to your collection, research the artist and determine the prints provenance.
Provenance is a detail of the past ownership, condition of a print, and where it has been displayed or exhibited. The more complete the history, the easier it is to establish the prints authenticity. Naturally, newer works are easier to document than older prints. Prints from the Smithsonian Art Collectors Program come with certificates of authenticity that itemize how, when, and where the prints were created.Although a full history that goes back to the time when the artist created the work is ideal, an incomplete history does not mean the work will not be considered authentic. Over time, paperwork can be lost or destroyed, or buyers may wish to remain anonymous.
If the provenance is incomplete, you might have an expert evaluate the print and confirm its authenticity, or at least attribute it to the referenced artist. If the expert determines that style and other factors make it probable that a print was created by a particular artist but cant confirm it, then the artwork will be attributed to that artist.
Experienced and trusted art dealers can provide authentication.
*From the Prints Buying Guide, eBay