How does one know that a certain Online Earning Site is not a SCAM?

Tweet

There are many sites that allows users to earn online by participating in activities that they hosts. These attract people to use the net frequently, in order to earn some money that could support them or just to have some pocket money. There are so much already that scams are getting into the system too. These are offers that people promised and got something from other people but never gave something back. In other words fooling around and stealing. Scamming sites are developing nowadays that they look so much like legitimate sites, thanks to the people having skills to develop web pages and stuff. It's like power going into the wrong hands. Does anyone know how to distinguished the legit from the scam online money earning sites before you can sign into it and give your credit card number? It's a problem nowadays, then again, no need for me to mention that.