[Elessar Telcontar]

I would have not given in to temptation and pride by emptying Mordor against the newly arisen King of Gondor. Surely emptying his his lands when the ring had yet to be found was foolish especially considering he knew it was not in the hands of Elessar, Gandalf etc.
In many ways Sauron caused his own demise by allowing himself to be fooled into letting his armies go into open battle at the Black Gate. In short Sauron should have believed his own weaknesses and ignored his pride...