You need to check for all the tell-tale signs, like being able to twist the metal top; you should not be able to turn it by hand if it is real. You should not be able to scratch the label off easilly with your fingernail either. Another common trick is the date. It should be obviously stamped on the bottle. Commonly, counterfeits have the the expiration date printed on the label in the same color ink as the rest of the label. It can be black but you can tell a stamp from something that was printed on the label at the same time the label was made. There is usually a dull area on the label where the date is to be stamped as well. Look for it. If it passes all of these tests, it is probably real. There are good counterfeits that will pass all these tests though, so keep that in mind. Just use your head and you should be fine most of the time.
