Telephone interviews are one of the initial methods to screen candidates. They are meant to be a relatively quick and easy way to narrow down the massive pool of applicants, before compiling a short list for on premise interviews.

Once you start sending out applications, be prepared for telephone interviews.
Practice your voice projection. Speak aloud to practice. Ask someone else to listen to you or even record and play yourself back. It's amazing how different you sound. You will notice the bad habits... the "errrrrrs" and "ummmmmms." Obviously, telephone practice as well as general interview and question practice are essential. Further, you should be able to demonstrate a good knowledge regarding the job, company, its' products and services and even its' competitors...that means undertaking research.
Here are a few tips worth refering