Credibility rests on both actual fairness and lack of bias and the appearance of those.
For example, when you look for a photo or artwork to accompany a post, make sure the image you use doesn't give the impression of your support or opposition to one of the issue you are writing about. Look at every illustration and word from the viewpoints of the most vociferous opponents of both sides of an issue.
For example, I wrote a piece about California Environmental groups teaming up with their enemies to oppose a proposition to require utilities to generate electricity from renewal resources.
If you visit that page, you'll see that I used a screen shot from a search of the National Defense Resources Council to illustrate a point.
I looked for an illustration from the sponsors of the proposal to use as a balancing graphic. But everything they had was "Yes on Prop 7." I could not use any of those graphics without implying that I supported Prop 7. So I used nothing from the sponsors.