It’s the way that people contact you when you are busy with other clients or customers, and cannot get to the phone. It is often the customers or clients first impression of your business or brand, you need to leave a great impression. The worst thing is for a first time caller, or even a returning customer, to get a short blurb like “Leave a message i’ll call you back”. Or, just a beep after the ring.
Hello you are talking to a machine; I am capable of receiving messages. My owner (your name here) does not need siding windows or a hot tub, and her carpets are clean. She gives to charity through the office and she doesn’t need her picture taken if your still with me please leave a message and she will get back with you.

First you need to know how much time your phone system or provider allows for the duration of the greeting. Some are 30 sec some are longer. Then you need to have a few ideas of what you want to say, or ask your callers.
10. "Hello, you've reached [X company]. We can't take your call right now, but please leave your name, contact information, and reason for reaching out, and one of our team members will be in touch within 24 hours.