I recently rejoined Mediabistro's AvantGuild because I was in the mood for a little professional development--I wanted to expand the roster of publications I was pitching to and maybe even take a class. Their "How to Pitch" articles are almost as good as having a friend at the publication who can give you the inside scoop, and they have a new feature called "Pitches that Worked" which is a very detailed dissection of how an idea made it to publication. Anyway, they're running a great, realistic piece right now that is relevant to all freelancers, called "What To Do When You Get Stiffed." To sum up: make sure you did the work and followed directions; make sure all your paperwork is in order, from contract to invoice (which should be complete, correct, and numbered); be gentle and cheerful, but firm and persistent, with your editor (or client) and take it straight to accounting when necessary. Be wary of taking on outlets (or clients) with their own financial difficulties, if you can't afford to lose the money. You should take your claim to a lawyer, the Better Business Bureau, or a professional organization for intercession only after several months have passed, and/or if you're really getting stonewalled. One person actually recovered her money by shaming the repeat offender in an online gossip column. This advice is great, but sometimes you just have to chalk these things up to experience. I am still owed a chunk from a time several years ago where I wrote encyclopedia entries for a small book packager. A fellow freelancer recommended me for the assignment, which I was very grateful for at the time, but we both ended up getting stiffed.