Or better yet, compose an e-mail to the person responsible and select the send and delegate option. This will send an e-mail and create the waiting for task. Plus it ensures that the person getting the task has a copy of an e-mail delegating the responsibility. I do this as a reminder, even if I've already talked to the person face-to-face., e.g. " per our discussion this morning, you will do /foo/ by /when/ ...." etc.