Perhaps the most damning evidence of a counterfeit site is going to WHOIS.net and typing in the URL. It'll then show you an e-mail associated with the account, and where the site is purportedly located. Check the technical and administrative contacts—do they match up too? Does it seem like there is a dedicated team of professionals solely dedicated to protecting this brand's space on the Internet? If it's in an obscure part of China or in a place that's totally not in line with where the brand is based, it's probably not legit.
1. Check the WHOIS