Having recently purchased 2 guitars, I was unaware they were fakes. Here are some tips to help you avoid my mistakes:

1. Fake guitars do not have traceable serial numbers if any at all.
2. Fake guitars do not have a country of origin stamp. If the seller insists its an offshore plant - verify this with the U.S. factory.
3. Look for design omissions. My fake Rickenbacker 370-12 strings lack the stereo feature noted on this model.
4. Look for design changes. My fake guitars have Gibson style metal covered pickups in lieu of the high gain toaster type for this model. Also, the trapese tailpiece is actually from a 6 string guitar that they doubled up on the paired strings in each mounting hole.
5. Look for design flaws. The neck on my fakes is too wide at the base where it connects to the guitar body. The result is that the strings are not parallel to the sides of the neck all the way down.
6. Check for propriatary design features. If you know that the Les Paul you want has a set neck and the guitar you are contemplating has a bolt on neck this should raise a flag.
7. Check out the sellers telephone number (call it) and  brick and mortar address. See if the telephone area code matches the business location. If not, he's probably using a cell phone and remote warehouse. Here today, gone tomorrow.
8. REview the sellers feed back rating.
9. I hope this helps you find that axe of your dreams without fear of being scammed.