Including unique product identifying codes in your listings is one of the most important things you need to do to make sure your listings can be found by search engines including eBay, Google, and Yahoo. Many items in categories including Home & Garden, Toys & Hobbies, Business & Industrial, and many others have unique identifiers such as Universal Product Codes (UPCs), European Article Numbers (EANs), International Standard Book Numbers (ISBNs).
Be sure to include the code for your item in the designated field whenever you list. See the location of this field for each eBay listing tool below.
It's also a a good idea to include the item brand name and the Manufacturer's Part Number (MPN) in Item Specifics whenever available.