Basically there is no sure way to get paypal to settle the dispute in your favor, but there are steps that you can take to give yourself a better chance.
The Paypal dispute team is just a group of human-beings who work off of their own scrutiny and methods. Granted they have some reservations and obligations set-forth by Paypal, but ultimately Paypal trusts their dispute team and doesn't ever question their finalized decision.


You're better off avoiding Paypal all together, but I will say that it's a sad day when scammers go unpunished because "the seller should have known better".