There are several things that you should do to prepare for a phone interview.
1. Temporarily disable the call-waiting function. The constant beeping would be an annoyance, and answering a call would probably lead to an automatic disqualification.
2. Take advantage of being at home. During an in-person interview, you shouldn't have your resume and other reference materials spread out in front of you; however, a phone interview affords you the opportunity to have these documents at hand, and these resources may help to prevent you from being stumped.
3. Remember to speak clearly and focus. It's easy to become overly relaxed when you don't have to face the interviewer, but don't fall into this trap. You may want to sit in an office-style chair to encourage attentiveness.