No, this isn’t meant to be insulting to anyone. But as someone who has listened to thousands of phone messages at work and at home, I wish there was a little more common knowledge on this topic. Here's what I wish that knowledge was:
1) The person you're leaving the message for is completely at your mercy. They can’t interrupt, or ask you to get to the point. So before you call, know exactly what you want to say (a good idea in case the person picks up the phone, too). There's nothing worse than listening to someone trying to organize their thoughts, except maybe listening to a person who forgot why they dialed your number in the first place.
2) I can’t count the number of times someone has called expecting me to recognize their voice. Say who you are immediately; this will help the listener start focusing in on the content of your message immediately, instead of wondering "who is this?" while simultaneously half-listening to your message.
3) Leave your phone number, twice. Saying "you have my number" forces the person to look it up, reduces the chance you'll get a call back, and may come across as narcissistic. Leave your number at the beginning of the message, then toward the end, in case they didn’t have something to write with the first time you said it. Speak slowly. Your number makes sense to you. To the listener, it's often "7mish25moshgish 332girsh."
4) Say why you're calling. This gives the person time to do whatever might be necessary to have an intelligent conversation when they call back. It's unpleasant, even frightening, to get the following message: "There's something very important I need to talk to you about right away." If you're calling a subordinate, it's especially important not to do this. Tell them what you need so they can start addressing the problem immediately.
5) Include any important details, or some humor if appropriate, but keep it short. A message that goes on longer than 30 seconds starts to irritate the listener because it seems to assume the listener has nothing else to do, and has nothing to say.
6) Remember you're talking to a person, not a machine. A phone message and a phone conversation are the same thing, only in the message only one person gets to talk. So greet the person as you normally would, and end as you would if they were actually on the other end of the line. Something simple like "Bye" works fine.
7) Relax. Many message systems give you the option at the end of deleting your message and re-recording. On the other hand, don’t assume you'll have that option- outline your message even rehearse if it's especially important.
8) If you're having trouble getting someone to call back, you can try breaking these rules. You can try being mysterious ("I have something important to tell you"). You can drop a subtle hint that if you don’t hear back, you'll assume they're on vacation and will try getting in touch with someone else (such as their boss) -- but without making this sound like a threat. If you express anger, it'll sound amplified to the listener, and will only give them an excuse not to call back ("well, if he's going to be that way about it, I'll let him stew."
9) If you and another person are both on the line and leave a message for someone you'd hoped to conference in, don’t torture the listener with banter between people already on the line. Both of you can say hello, but one of you should leave the message, then hang up.
I hope, dear reader, that for you, all of the above is stating the obvious.