I made my living as a freelancer for about 7 years. For the past five years, I've been the assistant editor or editor of a weekly newspaper with 27,000 circulation. I'm also the editor of a new monthly magazine and contributing editor for the past 7 years to another monthly magazine. About a quarter of my income is freelance now.
It's not always the same for every magazine, but you usually start with a query letter - send them an idea you have for an article along with your qualifications as a writer - where you've been published in particular. You can see examples of those kinds of letters in Writer's Market. You can sometimes submit multiple query letters, but you need to let everyone know that. Do the query first, then do the article once you have an interested magazine.
Depending on the market, a lot of writers I know take one idea and sell it to three or four different magazines and do seperate articles for each one. For example, a good friend is a music writer, and he'll do a profile of a band for one magazine, a concert review for another, a CD review, and maybe a 10-questions kind of piece with one of the band members for yet another magazine.
I've had about 20 magazine articles published this year, but I'm at a point now where I'm a known quantity with some magazines, so I haven't sent out a query letter in quite a few years. The editors just call or e-mail me and ask me to do the piece. They know what they are going to get. That's the best arrangement to work out.
PM me if I can be of help and I'll let you know how to get in touch with me.
S4