Well, start by ignoring any listings from China. Even if the phone is made in China, ALL the stock manufactured there is shipped to the Lenovo (or Apple, or Joe Fresh, or Louis Vuitton, or Prada) for shipping to their retail outlets.
So you can assume that anything sold directly from Asia is counterfeit, or a second, or 'fell off a truck'.
Then look at the price. Brand name goods have protected retail outlets and strong control on prices.
If the item is very low priced it is very likely to be refurbished (not necessarily a problem), an older model (not necessarily a problem) or once again stolen (big problem, especially if there is a warranty question.)
And of course, warranties.
Most warranties are from the manufacturer. Don't expect any warranty offered by an eBay seller to be worth anything unless he is also an agent of the parent company.
There are exceptions, for example, Henry's sells cameras here as well as in their chain stores. I'd trust anything they said. But a Chinese seller with several hundred negs (even if he has several thousand sales)? Nope.
