National Speakers recommend not answering your phone.
I have heard it from more than one national speaker, marketing consultant or coach that you should not answer your phone when it rings. You should have a system in place to handle incoming calls because you want to give the impression you are busy and successful. This system could be real-time voice mail or an assistant who handles your calls. When clients call this system allows you to call them back at your convenience. Theoretically, when you are not as busy and have more time to focus on this one client. This is how we professionals interpret how the process works. But what does the client hear when they get voice-mail or a receptionist.

"Hello, Mr. Realtor's office."
"No, Mr. Realtor is too busy and too successful to talk to you right now. If you leave a name and number he may call you back sometime next week. Of course, that house you are interested in may be sold by then but that is the benefit you get by working with a busy and successful person like Mr. Realtor."
"Thank you and have a great day!"

"Hello, thank you for calling Ms. Realtor's voice-mail. As you are probably aware I don't recognize you phone number and it was not important enough for me to answer in the first place. However, if you leave a message I might call you back in a day or two. That is if I think you can put some money in my pocket. Otherwise, I will continue to enjoy my afternoon at the spa."
Who are we really kidding here?
If you are not looking at this from the clients point of view you are kidding yourself. Especially, now a days when 84% (2007 NAR survey of home-buyers) of shoppers begin their search on the Internet. They want to talk to someone when the finally decide it is time to make that call. If you are not there to answer the question they already have a back up Realtor in mind. Remember, people today are doing the research for themselves. Do you really think they are not doing the math on the commission? Believe me people understand a million dollar producer is not busy.
Answer your phone.
Not answering your phone may have been good advice a few years back but technology (Caller ID) has made this practice obsolete. People expect you to have a cell phone and want you on their terms. I think voice-mail and receptionists are valuable tools when used effectively. However, how your client perceives these tools is what is important. Just because you answer the phone does not make you desperate. You could actually use it as your USP and create a niche. Niche: I only work with 2-3 buyer at a time so I can give them undivided attention and I will always answer my telephone.

I HATE leaving voice mails. If you answer the phone, then they feel you have time for them. That is what it is about, right? Customer Service!