The first step in creating a voicemail greeting is deciding what you want to say. Writing down your greeting is the easiest way to ensure that you do not forget anything vital or trip over your words when recording. If possible, ask someone else to listen to your greeting before recording it to make sure it is clear. You want to make sure your greeting gives clear instructions; otherwise, callers may be less likely to leave a message.
I just called a psychotherapist colleague and listened to her voicemail greeting with the now-ubiquitous message, “If this is an emergency, hang up and call 911.” My professional voicemail

"[Auto-attendants] assist a business of any size in presenting a more organized, efficient, and, if necessary, more robust picture of itself,” points out Brandi Armstrong, Co-Founder of Telecentrex and blogger on evancarmichael.com. The right greeting can make the difference between a frustrated customer or a satisfied one.
9.) Benvenuti alla John Doe. Siamo spiacenti, ma nessuno è in ufficio al momento. Si prega di lasciare il vostro nome e numero di telefono dopo il segnale. Vi richiameremo al più presto possibile.