Write 100 articles yourself, and after you've done that, then you'll know exactly what your looking for in content, and then you can easily then communicate this to other writers. Many people starting off just ask a couple of things like keywords.
I've now got a 200 word blurb that i copy and paste when i order an article and tweak it depending on what i want. It ensures I get the articles exactly as i want them, and leave no margin for error.
I got this blurb by writing the articles. Then ordering an article with no conditions on it. It was easy to spot all the differences and i just wrote them down.