Find some common ground. If you’re cold calling someone, your voicemail is your 30 second chance to make a connection and leave a good impression. One of the best ways to make a connection in that short amount of time is mentioning a mutual acquaintance. You could also mention a shared affiliation with an organization.
Think through what you are going to say before you place the call. When men hear the beep, they often freeze up and forget what they wanted to say. If you want to be the go-to guy at work, then you have to exhibit competence on all levels. Don’t spoil your confident image by hemming and hawing and filling your messages with “uhhhhs,” and “ummmms.” If it’s a really important call, consider writing out what you want to say beforehand. If the person picks up, great, you now have some notes to remember what you wanted to talk about. If they don’t answer, you can leave a clear and concise message.

A general voicemail greeting is what callers will be greeted with if you are unable to answer the phone at work. It is the everyday greeting, used as the default, unless you have set up a temporary greeting, such as an away message while you're on vacation, or a special message during a holiday.
If your auto-attendant starts with the main menu of options, it needs to be clear and have the option to speak with a human-being if the question isn’t answered by the list of options. Try something like this: