One possible solution must be studying about them and following them for long period of time will help us to get a clear picture on them. Still, a well planned a scam may go for a running for years.
Overall, risking very less amount would be the right way to have investments in others business.
If we know that those are the scams then why to invest even a small amount in it as they may give you returns at initial stage to gain trust from you and once you invest a bigger amount they will surely will not pay you anything and will run away with your investments, best investment is to hold your bitcoins for a long term.