Write articles for promotional purposes. Your aim should always be to get paid for your articles, of course.
Consider writing articles for:
* your local and statewide newspapers (the business section and magazines);
* Web sites. Check out the sites aimed at your target audiences. For example, much of my business writing is for the construction and heavy equipment industries. When I check out the Web sites of most of the companies, I see that most are simply lists of equipment, with specifications.
I could spend ten minutes asking myself what these company sites need. They need: a company overview, an interview with the CEO, customer testimonials, press releases, and articles on training. I could write to these companies, offering to do the above writing projects. I would get paid for these projects, and I would ask them to list me as their copywriter with my contact details somewhere on the site.
In the past, I've suggested that you should write free articles for Web sites for promotional purposes, and you can do that. However, please look at ways to get paid for your writing efforts first, even if you're writing for promotion. If you have any time to spare, you can write for free.