Most counterfeit perfume purchases can be avoided by going to a reputable seller. There are a variety of outlets for perfume, and it’s important to understand the benefits and dangers of each.  Department stores are always the safest way to buy perfume, as you have the advantage of being able to closely examine the bottle in its packaging and talking to the retail staff. This allows you to approach the staff if it’s possibly a fake, and you are able to return the perfume if it’s not authentic. Be very cautious at flea markets or swap meets where sellers can easily rip you off without recourse. Always carefully inspect the perfume before you purchase it, and if at all possible get the vendor’s contact information in case it turns out to be unsatisfactory. Feel free to ask the buyer very direct questions based on the information explained here. For example, "Can you please tell me the batch number?" and "Can you put up a photo of the text on the back of the box?", etc. When buying online through eBay or Amazon it’s important to check for product and online seller reviews. Make sure the seller is PayPal verified as this means they had to disclose their contact information. Check to see if they have a return policy, and demand one if they don’t. Pay attention to whether the listing is written with proper grammar and spelling. Although this isn't always indicative of the quality of the perfume, if it's really cheap for the "brand" it claims to be, then it's likely to be too good to be true and it isn't the real perfume. There may be exceptions, such as a stock clearance where a store is closing down, but on the whole, the price provides a good indication of authenticity. Check the manufacturer’s website to see if they have provided sufficient information on the packaging, bottle and the placement of the bar code. You might want to visit mall stalls to see how the bottle and cellophane wraps look on the authentic perfumes to get a good idea of what to expect.

TL;DR in Chinese:
了解卖方。 注意价格。 事先对香水进行研究。