Thank you for these tips. I would also like to add mine, based on my experience as an SEO writer.
Writing effective content means good research. You have to offer something new and fresh to the table. You can only do that if you've researched hard enough to see different facets of your content.
Another thing that I would like to highlight is presentation. Writing good content means nothing if people won't read it. A good presentation attract your viewers to read your article in the first place.
For presentation, no sentence should be 20 words. Writing must be casual, direct, and simple. Think as if you're writing to a grade 4 student.