Many block cipher modes require an IV. The IV is required both for encryption and decryption. If Alice sends Bob a message encrypted in a block cipher mode that uses an IV, how can Bob know the IV? If...

Many block cipher modes require an IV.
The IV is required both for encryption and decryption.
If Alice sends Bob a message encrypted in a block cipher mode that uses an IV, how can Bob know the IV?
If you know of multiple secure solutions, please mention them all..