If you've ever skipped a voice mail or decided to listen later because it rambles, you're not alone. Too many people don't know how to leave a voice mail message, says Ken Taylor, president of Decker Communications, San Francisco. His advice: limit voice messages to less than 30 seconds. But prepare what you want to say ahead of time, so you can still provide enough detail to allow the message recipient to understand what you need and by when. Above all, limit yourself to one subject per message, and recite your phone number slowly.