You can search this forum with keyword "fake". There are so many discussions regarding this topic already.
If you have trouble to figure out which one is real, then only purchase through reputable stores. Ebay seems a no-no, as it's been flooded with fakes. Only a few of ebayers selling real stuff these days.
check bluejeff's list of ebayers who have proven to be reputable. i think sumai03 and tum98 are the 2 of the most frequently used genuine racquet sellers ...