Plan your story. Get the background of the story before the camera starts to roll, unless you are covering breaking news. Find out as much about the story from the subjects, victims, witnesses, authorities and other people as possible when you call to set up interviews so your on-camera questions are more intelligent and to the point. Outline the story, making sure that the five "Ws" of journalism are answered: Who did something? What did they do? When did they do it? Where did they do it? Why did they do it? Remember that in most cases, television news spots are seconds long rather than minutes long.
Remember that you are not the star of the story. Let the subjects you interview tell the story as much as possible, interjecting your own voice and words only when necessary, such as your introduction and wrap and to fill in important details that you were not able to get your subjects to say. Make it your goal "to get out of the way:" Emmy Award-winning Baltimore reporter Mike Schuh says, "I just want to say as little as I can to set up what they're going to say so what they say makes sense and adds to the overall story."
Keep your language conversational; use your introductory sentence to grab viewers' attention and then begin laying out details. Write the story with words supplementing pictures, not with pictures supplementing words. Refer to your images, but don't describe them if the picture speaks for itself. Budget most of your words to say what your subjects and pictures don't say. Don't waste words telling viewers the name of someone unless it's important for them to know that person's name. Use subtitles to identify subjects otherwise.
Edit your story to synchronize your words with the images, making sure the pictures change precisely when you refer to them. Avoid self-serving shots of you listening to a subject answer your question, or otherwise injecting your image into the pictures unless it's necessary.