If it is your personal cell phone or land-line it is a good idea no matter how you are feeling to answer with a fairly cheerful voice. If you are busy excuse yourself and promise to get back to the person as soon as possible and do just that. Not answering any messages left to you on your answering service in good time is poor telephone manners even if all you have to say to the person is you got their message; you're busy and you promise to get back to them at a specific time. When answering phones at the workplace (if you are a receptionist) you should answer the phone with a cheerful voice; name the company and in some cases your first name. Take messages for management or coworkers and be sure they get them. If you own a business it is smart to treat the smaller clients just as well as the larger clients by answering any messages you get or answering any questions they may have.
