Who decides what stories will be printed in the Monitor? Who picks the stories for the 10 O'Clock News on Channel 2? Journalists make those decisions, and when they do, they are performing their "gatekeeper" function. They decide which stories to let through the "gate" and which to toss into the trash.
Journalists decide which stories are important enough to run on page one, and which ones run inside.
But the gatekeeper function also affects the way we write our stories. The reader looks to the journalist to make sense out of a confusing world. It is the journalist's job to find out what's going on, then choose from a notebook full of scribbles only those facts necessary to give the reader a clear, concise picture of the most important events. Obviously, this process leaves some facts out of the story. You must be sure that your story includes the most important information.
But for you to make that judgment, you have to learn everything possible about your subject, and that means you will end up knowing a lot of less-important facts that will never make it into a news story.
A good reporter loves to dig into a story. The rule is: "Write 10 percent of what you know."