I'm looking for some advice on what makes a good advertorial? Specifically how it should be branded, how the article should be formulated, how salesy it needs to be vs looking like a genuine news article.
Thanks 
A good advertorial looks and reads like an objective news article. However, there is no set standard for advertorials. It depends on your product, your demographic, and the type of sites you are advertising on.
If you look at sites like foxnews.com you can see live examples of advertorials. Just scroll down the "outbrain" ad widget.
Companies like Babel have got it down to a fine art. https://www.babbel.com/en/magazine/l...age-20-minutes