Rather than waiting for a callback, open up additional channels of communication with your callers by inviting them to email. The most professional voicemail greetings often include an alternative method of communication.
Responding to voicemails is time-consuming. Fortunately, with the right greeting, you might be able to save yourself some hassle. If you don’t have an auto attendant, you can give callers the information they are looking for with your voicemail greeting. Of course, this means that your greeting may be a little lengthy, but that can work in your favor as callers will only stay on the line to leave a message if they still need assistance.

A word of warning: These greetings will not do you any favors if you're in the midst of a job hunt or work in a conservative industry. Always remember your target personas. If there's a chance they won't appreciate your sense of humor, opt for a straightforward greeting instead.
It is important that the voicemail greeting be brief but also action oriented. Do you want your caller to leave you a message? Or perhaps they should call another extension to reach an assistant or office manager in your absence? Get to know the business phone system that you are using and take advantage of its features. Some phone systems allow the caller to press a digit, such as 0 to transfer to another extension rather than having to end the call and dial another extension. This type of function can be extremely useful, especially if other people in the office can handle the calls that are incoming to your phone while you are away from your desk, or out of the office.