Magazines have folded by the dozen since the economy started its now infamous nose dive last fall. But most didn’t disappear overnight. Over the months, observant freelancers learned to read between the lines for signs a particular publication might be cutting back or, alas, shutting down completely.

Here are some indicators that all may not be well, based on my personal experience and with the help of some fellow freelancers on my favorite writers’ message board.

You know a magazine is in trouble when…

1. Emails to the editor you’ve been working with on an assignment suddenly bounce back, her voicemail is full and she’s not answering her phone.

2. They aren’t assigning anything new for the foreseeable future and are using up their backlog of already completed – and paid for – stories instead.

3. They’re using staffers – and editors – to write everything.

4. They’re using consultants, analysts and other industry experts to write columns instead of freelancers.

5. Instead of professionally written stories, they’re using message boards and other user-generated content to flesh out their Website.

6. They’ve switched to paying on publication instead of on acceptance.

7. They ask you to send a self-addressed stamped envelope along with your invoice.

8. Instead of sending your invoice to the lowly editorial assistant who’s handled the task forever you’ve been directed to send them straight to the assistant managing editor.

9. Invoices that used to be paid within 30 days or even less are now paid in 45 days – if you’re lucky.

10. They ask you to accept a smaller fee or lower per-word rate than what’s stipulated in your contract in order to get paid.

11. They love your story but hold it for a month for budget reasons and, despite the payment terms spelled out in your contract, demand that you to hold off sending an invoice for a month too.

12. They can’t find your invoice – again.

13. The latest issue comes in the mail and you mistake it for a promotional brochure.

What warning signs do you look for?

For a great take on what’s happened to the U.S. magazine business over the past dozen years, be sure to catch Washington Post staff writer Peter Carlson’s latest and last entry in his column, The Magazine Reader.

Carlson’s finale is titled “Looking at 12 Years Between the Covers”. In it he chronicles the magazines that came and went, and a few trends that hit the business during his 12-year tenure: the Maxim-ization of U.S. mens’ magazines, the onslaught of “me” magazine also-rans that followed in the wake of the very successful launch of O: The Oprah Magazine, and the comforting constancy of the sex tips that run month in and month out in women’s glossies like Cosmopolitan and Glamour.

Carlson, who chronicled the ups and downs, start ups and demises of American magazines, is taking the Post’s early retirement buyout and “heading off to pursue other interests, such as sloth and gin,” he writes in the article.