Instructions
Turn the item upside down and check the base, especially the rim. Does it look metallic? Give it a tap and listen for a clinking sound. Cloisonne is applied to metal bodies, usually of copper. If your item is made of pottery or wood, then it's definitely not a piece of cloisonne.
Inspect the design itself. Shapes and details should be demarcated with a pattern of wires -- chunky and easy to spot on lesser pieces, extremely fine on the best wares. Once-bright silver wires go dull over time, so look carefully. If you're item has passed Steps 1 and 2, then it's almost certainly a piece of cloisonne. Steps 3 and 4 will help you to assess its quality and place of origin.
Take a step back and consider the design from an aesthetic standpoint. Is it a series of abstract patterns, perhaps with some stylized flowers? If so, then the piece is most likely of Chinese or Middle Eastern origin. Or does it portray a naturalistic scene, perhaps a bird such as a wren or sparrow perched on a twig and surrounded with a spray of flowers? If this is what you see, then you're holding a piece of Japanese cloisonne.
Examine some of the individual cloisons. Rather than being uniform blobs of color, cloisons on the finest Japanese wares often display delicate shading.