Think before you speak. Ramble on, and you just may get cut off. So start your voice mail with an overview. “Map out” the reason you’re calling and then add any relevant details. Preparing in advance also means that if the person actually answers, you’ll be ready to talk.
Start with the numbers. Leaving a phone number is the “most critical” part of the call. Be sure to mention it at the beginning of the message, so the person “won’t have to replay the whole thing just to jot it down.” Just to be safe, say it again at the end, and enunciate clearly both times.
It’s not about you. It takes two to have a conversation, even when you’re just leaving a message. Whether the subject is business or personal, try to express “what is in it” for the person. If the topic is genuinely complicated or sensitive, don’t leave a voice mail at all. Call back.
Source: Allure