• They hire you on the basis of an email or phone call, without any personal interview or background checks. That's not how legitimate companies operate.
• They ask you to help process payments by depositing checks or money orders intended for their company into your bank account. You send them the money and you keep the extra as your "pay." Real companies, even those in other countries, never operated in this manner. They have payments go directly to their own accounts.
• They ask you to be a "mystery shopper". You send funds from a check or money order to "test" a money transfer service or buy several small items at a store and send the rest of the money back to them.
• Legitimate companies would never ask you to use a money transfer or delivery service to send cash to them or anywhere else, for any purpose.