Beware of schemes in which recruitment of new members is more important than the product being sold. Whenever in doubt, wait until you can consult all available resources. Never send cash through the mail or give it to a messenger sent by the salesperson, and never give a credit card number over the phone. Keep all correspondence and take notes of all conversations regarding an investment. No legitimate broker will rush you into an investment.
High pressure is a good indicator of fraudulent operations.
Beware of testimonials. Fraudulent companies sometimes hire people to claim that the firm's investments brought them wealth. If in doubt, do not invest. It is better to be safe than sorry. Also, if you become suspicious, get out of the investment.