Once there was a little boy who heard from his mother that his grandmother was sick. So he called his grandmother, and she was really happy, and she told him to call her every Friday. And then he told his friend, and she was inspired to call her grandmothers. And then she told her friend, who was inspired to call her grandmother. And eventually each friend told a friend, and these people told their friends, who told their friends, until everybody in the town had called their grandmothers, and all the grandmothers were happy. And the moral of the story is: mitzva gorereth mitzva.
(Now, in fact, the people involved in this story in real life were actually not little children, but adults. But that hardly changes the message.)
Call your grandparents! It is very easy, and it will make them very happy! And spread this message to all your friends!