I am not in the office today; I may not be in tomorrow. I may be in to work sooner, if you gave me your car to borrow.
The business answering machine greeting you use should be fairly short and to the point, though you can use it as a way to demonstrate what your business has to offer. Your overall tone in the message should be professional and indicate to callers that though their call has been missed at that moment, they are important and you plan on contacting them as soon as possible. Within this, however, you should not indicate that you are talking to someone more important than the caller. Your business answering machine greeting should also be customized in any way you deem appropriate for your business and needs. Jotting down the greeting will prevent mistakes when recording it.

When you leave a voicemail do not use your full name because that immediately raises a red flat that you are a salesperson making a cold call. Instead, say your first name only followed by your company name. This will make your customer feel that you are much more familiar with each other than you really are. Saying your last name would defeat the whole purpose of demonstrating familiarity.
Greetings. You’ve reached the office of [Name]. I’m either out of the office or gone for the day. However, your call is extremely import to me, so I’d appreciate it if you’d leave your message, along with your contact information, at the sound of the beep. Thank you for your call.