When writing articles that require interviews and research, itís important to seek balance if the topic is controversial, unless you intend to write a slanted piece.
To understand the concerns about balanced sourcing in a real world situation, consider the recent political race involving Mitt Romney. This candidacy has led to a great many articles about his religion. He is a member of the Church of Jesus Christ of Latter-day Saints, the Mormons. Members of this religion have protested that while they appreciated the attention given to their religion, the press had developed the habit, when writing about doctrine or Mormon people, of interviewing everyone except actual Mormons. The experts quoted are often people who have never been LDS, which is similar to doing an article on how women feel about motherhood and interviewing only men without wives or children. While they might have a lot of book learning on the subject, they canít begin to understand how it feels on the inside.
Others interviewed were former church members, who would clearly have bias and perhaps an incomplete understanding of the religion. This might be like interviewing a popular hate group about the people they hate and calling it an unbiased article. A person who no longer wishes to be associated with an organization or religion is clearly going to see and report the negatives, and may, depending on their history and ethics, choose to lie.
Missing from most articles is actual Mormons. This means the writers may well misinterpret the information they are seeking because they didnít interview any of the actual participants. They need, in addition to those other sources, some people who choose to live the religion and who care about it.
Having a mixture of the three types of sources allows readers to see the topic from all points of view and to be sure the focus and worldview are accurate. They are then free to make their own decisions, if youíve presented the information fairly.
When using sources, be certain to identify them. In the above situation, if the person you interviewed was not LDS, you would say so. Leaving out this information prevents the reader from evaluating possible bias on his own. If he is an official spokesman for the religion, you would also note that, since it will influence what he says.
Go to your favorite news source or magazine and read a number of articles. See if you can identify bias in the articles. Check the credentials of the sources yourself and compare them to those given by the writer. This will teach you how to evaluate sources in your own writing.