The first and foremost way that I have found to earn money is by using Google AdSense! I use it on social networks that allow it's usage and also on webpages.
You earn on a pay per click basis, but let me warn you that if you try to cheat them, you will get caught and lose your earnings, so be sure to go about using the ads honestly and you will earn!
You see ads all over the internet and most of them are from Google. Every time you click on one of their ads, someone is getting paid. Why shouldn't you?
My suggestion is that you join Google AdSense by clicking on the box above this text and get on your way to earning from the internet!