My method is a careful research. I investigate documents, web-sites, partnerships, audits, community, social media. Also I rely on some bloggers that give their own opinion. I know that it is impossible to protect yourself from all scams even if you investigate it carefully as there are some scammers who act very sensibly, so it is difficult to identify their fraud, so the main thing is to comply with risk management and not invest more than you can afford to lose.