Generally speaking, I've never had difficulty writing a news story.
Usually, like many things, the hardest part is getting started. For journalists, that start is called the lead. To the layman, it's probably better known as the introduction – usually a couple of sentences, sometimes a couple of paragraphs.
And for me, hard news typically has written itself. I can't tell you why except perhaps to describe it as if gathering the information for a story is, for me, like focusing a camera on your subject. Once I've gathered the information, the image is clear and I write.
But feature stories – stories that are not necessarily news, but perhaps paint a portrait of an individual, a family or institution, or even an event – those are the ones I've struggled with most. They also tends to be the stories that are in many ways most rewarding.