Part four in the series:
Will you write me an article on X so I can see a sample of what you will do? I'm not going to pay you for it or use it, I swear!
I fell for this once. I wrote some beautiful ad copy for a potential buyer and they didn't take it. now I use it as a sample, but otherwise it's useless. I wasted my time. Would you ask a store to give you $50 of product so you can make sure the quality is good? I have plenty of writing samples to show my quality of work. I will work with you to make sure you are happy with the end product. Don't ask me to work for free!