First, you must master writing. If you're writing articles, then master the writing of articles. Read the best articles, online and in print magazines. Read books about how to write articles. If you're writing print articles, read about how to write for print magazines. If you're writing for the web, read and study web content and writing for the web. Write with clarity and interest.
When you have mastered the art of writing articles, nonfiction or creative nonfiction, then decide what areas you want to master in knowledge. Perhaps you want to write business articles? Perhaps you want to write film or music reviews? Perhaps you want to write expertly about fashion or food or gardening.
Learn as much as you can about these subjects. Read books on these subjects. Read articles on these subjects. Keep a catalog of up-to-date information on these subjects. Interview experts on these subjects.
When you write about these subjects, even if you're not an expert yourself, you can quote the experts. You can co-author with the experts. You can have the experts read your article and give commentary.
Go to lectures on the topics that you're interested in writing about like an expert. Take workshops in the topics that you're interested in writing about like an expert.
Write like an expert. Perhaps you'll learn that in writing like an expert, and mastering the art of writing like an expert, you become an expert in these subject areas.
