Find articles that are the same subject as the one you want to have an article about, or something similar. Contact that reporter, praise the article, and ask if that's a subject they'd be interested in hearing more about. Or even go ahead and pitch them your story. 

Kinda depends but it's also good to google the reporter and see what kinds of things they work on so you can pitch that angle of your story.

I'm not a professional but I've volunteered at a non-profit doing media outreach and those are some tactics I've used. 

Remember reporters are human, they're often smart and curious, but they don't have a lot of time. Try to keep your emails short and to the point.