Many of the articles you read in magazines started with a writer pitching an idea to an editor. The field of freelancing has a few land mines, particularly for first-time writers, so you'll need to watch your step.
Find out if the magazines you'd like to write for accept freelance submissions. Although it's becoming more rare, some publications still are exclusively staff-produced.
Match your idea to the publication. Identify magazines that would publish the kind of idea you have in mind. Read several back issues of the magazine(s) or check the online archives to get a feel for the readership, the topics covered, and the general tone of the articles. Be certain that the magazine hasn't covered your idea in some fashion already. Also, look closely at the length of the articles and see if it fits your style.
Turn to subscription databases like Wooden Horse Publishing (woodenhorsepub.com) and Writer's Market (writersmarket.com) for more in-depth guidance regarding what the magazines are looking for and how they want to be contacted. Writer's Market costs less than $50 per year and Wooden Horse is about $150, but both are excellent information sources.
Review editorial calendars, which are often featured on magazine Web sites. These give advertisers, readers and writers a headsup regarding planned issue themes. Keep upcoming topics in mind when you're pitching, and be sure to mention the particular issue to which you think your idea is particularly well suited.
Think at least three months ahead--the minimum time table most magazines work under. That means you'll need to pitch Mother's Day ideas in January or February and back-to-school subjects no later than May.
Avoid the biggest rookie mistake: sending a finished, unsolicited manuscript. Instead, find out how the magazine accepts article ideas. Ask to see a copy of its writers' guidelines and follow them to the letter.
Pinpoint the best editor for your idea. If need be, call the magazine and ask which editor is best to contact, and how he or she prefers submissions (via e-mail or conventional mail).
Craft a one-page query letter. Identify the specific audience that may find the article interesting. And cite any statistics or research that support your proposal.
Include three clips (photocopies of actual articles you've written as they appeared in a publication) with your query letter. If the magazine is of general interest, submit a variety of clips; if it focuses on a particular topic, include clips that show your expertise in that area.