Author Linnea Sinclair shared this great promo tip with me. When she's writing a new book, she notes great "clips," small snippets that tell a sort of mini story or make a great teaser. She copies them into a file marked, "promo tips for book XXX" and then gets the file out when she ramps up the promo engine. She randomly copies the clips into the signature file for her email and "teases" readers until the book releases and beyond.
It certainly worked to get me to read more of her work!