Fakes are more easily available than original luxury products. Check the following to identify fakes:

Price: A small Chanel quilted bag costs $650. If you're buying one for $40, or even $250, you're not getting the real thing.
Location: Louis Vuitton, Christian Dior, Prada or any other luxury product is not sold anywhere but only at authorized dealers.
Detail work: Pulled stitching, cheap linings, banged up hardware, crooked or misspelled logos are all telltale signs of imitations.
Tax: If you're not paying tax, neither is the dealer.
Origin tags: Luxury products like Chanel, Fendi and Gucci are not manufactured in China or Taiwan.
Plastic: Super expensive bags do not have their handles or hardware covered in cheap plastic.