The answer is online reviews.
Using a search engine, you can search for millions of articles (just like this one) which review these opportunities. This is the most effective way of finding such articles, and the best way to find information about online job opportunities. Basically if one of these programmes are a waste of time and money, people will be talking about it.
There is one problem however, many of these "scammers" are very clever, and pay people to write "testimonials" or articles promoting their scheme. Therefore the most effective way is to find a site devoted to reviewing online job opportunities, allowing you to find an online job for you without having to worry about being scammed.