making money online

I heard from a friend about these sites that allow you to earn money simply by answering surveys or posting on a forum and was shocked.
How legitimate are these sites and where do you find the good...

cashcrate legitimate?

I recently joined CashCrate, but now I wonder if it was a mistake.
All of the offers on the site look like scams, with a lot of fine print at the bottom of the page.
How do I know which of these...