[drcy]

You can usually tell by the wording. "My local card shop said it looks real but according to eBay rules since it it is not graded I must sell it as an reprint" and is wording from someone who knows it's crap. I've more than once said you can often identify a fake by reading the auction description and not even looking at the images.

You can also tell by messaging that the item is a fake and observe how he/she reacts. I had someone who said he didn't realize and removed the auction-- obviously an innocent person. Others just ignore you or worse.