1. Read about ten of the magazines you want to write for before even attempting to think of what to write for them.
2. Then go online on their website and look to see if they've issued a "call" for a certain type of article.
3. Start small. Sometimes in order to "break in" to a magazine you have to write for their smaller regular columns at the back of the magazine.
4. Carefully look over the magazine and decide who their audience is, what kind of articles they like, and then see if you have a story or helpful tips that fit their customers.
5. Write a short letter to ask if they are interested. Find a "need" of their audience, and explain how your article will help solve their audience's "need."
6. Look up statistics. For some reason my queries always get accepted when I include statistics.
That's it! Hope it helps. Magazines are really marketing tools that are preaching to a certain audience, so if you keep their audience's needs in mind, and you write in their 'style', you'll probably have success.