If you want to be famous or reach a wide audience, you will have to choose something slightly broader and work hard to make the best content for that topic. A subtopic relating to fitness, finance, or relationship advice is likely to reach the most people. Consider specific but broadly applicable topics such as managing money in college, or a marriage counseling blog.
If you are interested in covering a broad topic that many people already write about, create multiple specialized blogs instead and link between them when the subjects overlap. For instance, if you are a nutrition expert, write one blog about healthy weight management, another one about child nutrition, and another about growing your own vegetables.
Create and customize your blog. If you are using a free service, there should be a tutorial to guide you through the initial steps of setting up your blog, as well as a forum for people to ask questions. If you are hosting your own site, you will need someone with web design experience to customize your blog, or you can use software such as WordPress.org to use the same structures available at free services.
Think of new article topic ideas. I have a long list of over 100 possible article topics that I keep on my laptop as well as on my phone. I think of the many, many topics that you'll find on Making Sense of Cents through life experiences, reader questions, research and articles that I've come across (like if I see a crazy statistic that I find interesting, I'll then turn it into a long article), and so on.
Some blogs are focused on getting paid to provide links to news articles, company stores, or other third party websites. The most financially successful of these range from the Drudge, a blog composed almost entirely of conservative-leaning news links, to Smashing Magazine, a site that provides advice and product reviews to help software developers.