Answering surveys was one of the methods that worked for me.
For taking a few minutes out of my day to answer a few random questions, this survey awarded me with a $750 PayPal Gift Card.
I was doubtful at first, but I figured there was nothing to lose by giving it a shot. And with that, I was able to earn money through PayPal.
There are numerous surveys available that can provide you with the same information.