The Assoc. of Certified Fraud Examiners has a useful list of red flags of Ponzi schemes.
#1
Sounds too good to be true. If an investment sounds too good to be true, it probably is. This old saying is perhaps the easiest way to spot a Ponzi scam.
And some of the perhaps less obvious red flags.
History of consistent returns
High-pressure sales tactics
Pressure to reinvest
Complex trading strategies
Read the whole thing. It might save your financial life.