The best way to protect yourself against online scams is to learn about them. Here are three web sites that report scams. By browsing these sites a little each week, you will become knowledgable about these scams and learn to recognize when someone is trying to pull one on you.
Check out Learning About Online Scams at YouTube for closed captioning and more options.
Snopes Top Scams Page
Reddit Scams Subreddit
On Guard Online
Another common scam is when you get a caller who claims to be from "Windows Technical Support" and tells you that they have been receiving reports that your computer is downloading malware. If you ask them why they would know anything about what your computer is downloading, they will tell you that it is part of the support service you receive for your Windows system. They will then try to lead you through some steps to show you that you indeed have malware. Hang up ASAP.