Maybe it is a stupid question
just use google as tom suggested (for future reference, mac, et. al. answered your question)
look for things that may indicate a legit. business (country of origin, physical storefront, you can even call the business authority in the country/city of origin, etc.)
if you're still suspicious for good reason, don't buy. if you're suspicious because you are buying something off of the internet, pay w/something that you can easily challenge the purchase with (paypal, credit card)
