I can't stand doing phone interviews, I don't know about you. Even though they're probably they most common way of contacting a source, I always feel so fake and think I sound so stupid, plus I hate those awkward pauses where you try to write down what the source is saying before you ask them another question.
About Freelance has some good basic tips on how to make your interview a successful one. It's important to remember that you're just calling to get information, not to show someone how charming you are. Some good nuggets include:
Keep a log of all the calls you make. Note the dates and times so you can deduct the long-distance charges from your business taxes. (The article includes a phone log you can download if you wish).
Find out what the law on recording telephone calls is in your state. You may be required to ask your interviewee's permission before taping the call. Tell him you want to be sure your piece is accurate when quoting him. If in doubt, ask your interviewee if it's okay.
Be a professional. A crying baby in the background doesn't send a professional image when you're trying to interview the president of a company. Eliminate the background noise and be sure turn off the radio or TV and disable the call waiting too.
By the way, if you're a slow writer like me, you might want to invest in a hands-free device and type your notes up, which also makes it easier for turning your notes in, should you need to.