Don' let background noise do the talking for you. Ambient noise on your recording could be sending the wrong message to your clients. The sound of your kids arguing in the distance could be the sign of a distracting work environment. Clinking glasses and restaurant chatter may leave the impression that you don't take your work seriously. When you record your voicemail greeting choose a quiet spot free from interruption, so your message is the only thing callers hear. It's also good to avoid large, cavernous spaces where sound verberates.
@Fa5t3r - I would try a wide range of different tones when recording and play them back to see what goes over the best and what projects the image you want people to hear. Remember that some people may be going to hear this message over and over again depending on how often they have to call you so you want it to be very pleasant and not at all irritating.

However, do not waste the caller’s time. They may hang up if they are forced to listen to a needlessly lengthy and uninteresting voicemail greeting.
Don’t be too hard on yourself. Chances are, that voicemail that you’ve recorded and deleted thirty times has been just fine. Your main goal is not to get in the way of the caller leaving a message, which is exactly what can happen if you overthink it or drone on too long.