Seller: Before picking out your wallet to pay for Nike shoes online, check the reviews and feedback by buyers first. It is mandatory if you are not purchasing from an authorized dealer. Another best alternative is to visit official site of Nike store and purchase from there. 

Compare The Prices: It is one of the most obvious signs of fake Nikes, they have an irrationally lower price tag. If you shoes being offered are ridiculously low priced, it is time you check out with other sites. The ones being offered here are probably fake ones. Start asking questions the moment you see the prices slashed by 50 percent, that will never be the case with original shoes. The price may go down up to 40 percent, but flat 50 + percent off sounds fishy. But if one such clearance sale in taking place on official store or site of the company, then it is a completely different thing. 

Check The Box: All Nike shoes are sent in labeled and tagged boxes. The print and color of the box will differ from the style you will be purchasing. However, the most common boxes used for this purpose are the red, brown, and orange ones. The side of the box should clearly show the bar code, SKU number, size,  and style. Anyone copying it might try to imitate the boxes but would not have the essential print thing on the side. There are some online sellers too that are included in sale of fake Nike and mostly ship those in plastic bags without any box. It is another tell-a-tale sign that those are fake. 

Check Style: A online seller Sneakerahead suggests that in order to familiarize yourself with details of Nike it is better to do some research on a prior basis. You can always check out the official Nike website and go through the products.