Future Hiro's message
The Message is
Save the Cheerleader, Save the World.
Future Hiro travels back in time and tells Peter Petrelli the message, and asks him to pass it on to the present version of Hiro Nakamura when he calls. Peter receives Hiro's call at Isaac's, and tells Ando (who translates for Hiro) about his encounter with Future Hiro, and delivers the message as promised. (Collision)
Peter is convinced that one of Isaac's paintings holds the key to the puzzle. Before they can "save the cheerleader", they must first find her, and Peter feels the missing painting from Isaac's set is the answer. (Hiros)
Hiro and Ando discuss the message at Union Wells High School after its Homecoming disaster. Ando suggests that the message is actually two separate statements, "Save the cheerleader" then "save the world." Hiro states that the message is an "if, then" statment, not two separate statements. (Fallout)
Fan Theories
Please refer to Theory:Future Hiro's message for fan-created theories and other speculation.