Prepare your questions in advance. Know what angle you want to take on the article, and tailor the questions accordingly. This eliminates awkward pauses in the interview while you rack your brain for something else to ask.
Do your homework. Time is precious in the newsroom, but spend 10 minutes online researching your subject before heading out the door. It helps to ask intelligent questions, and it shows your subject that you're genuinely interested in the piece you're working on.
Check your hardware. You should have at least two pens to write with, enough blank pages in your reporter's notebook and serviceable batteries in your tape recorder. Print out directions before driving to an interview and a phone number to call your interviewee if you get lost or plan to be a few minutes late.
Be punctual. This is professional and shows respect to the person who has invited you into their home.
Express your sympathy at the door if you're talking with someone who has lost a loved one. These are difficult interviews, so it is best to be polite and let the person talk at his own pace.
Pick something in the house to talk about as you set up your notebook and recorder. This sets the interviewee at ease and might even reveal some interesting facts about the person for your story. The same applies if you're talking to someone in an office, which usually has a scattering of awards and trophies or at least a family photo.
Don't interrupt. You'll probably think of a few questions as the person talks, but just write them in your notes and come back to them when the person finishes talking. Your job is to listen and observe.
Thank your subject for her time as you leave, and ask her if it would be OK if you call later with follow-up questions.