I don’t know if I’m good at my job. I cannot point to something in the physical world and say “yes, that is a well-stacked pallet” or “I was as efficient with slicing as possible.” (I worked in grocery stores prior to my current employment. I was very good at that job.) I only have my subjective judgment, and that’s not great because I’m super biased towards the way I think and express myself. Writing does not have inherent, objective tests of quality, so I want to create some, and to do that, I’m going to look to another passion of mine: cooking.
In cooking, the highest honor a chef can receive is three Michelin stars. A restaurant with one star is very good in its category, with two it's worthy of a special detour, and with three it has food worth an international flight. We know of five specific criteria that make a restaurant worthy of a Michelin star: quality of the product, mastery of technique, personality of the chef in the cuisine, value for the money, and consistency between visits. With a little modification, these make for a good starting point for quality assurance in writing.
This one is pretty straightforward. If no word, clause, sentence, or paragraph stirs an emotion or creates a new thought in readers, there may be an issue with your writing. Starting with the diction and expanding the scope of your examination until you’re looking at the paper as a whole can help improve your writing quality.
This is seen as the boring stuff. Good writing shows a control over grammar, word choice, punctuation- all the stuff that English majors and English majors alone know the names of. It’s okay to not know the term "comma splice," but it’s another thing entirely to not know what a comma splice is.
Academic writing has a certain sound to it. It’s often impersonal and dull, but it’s okay to have some of your own voice in your writing. It’s your writing after all.
Is your writing saying something that’s worth the time it takes to read? If you’re writing a tweet, then you don’t have to say much because your writing only takes a few seconds to read. If you’re writing a book, your argument has to expand and be worthwhile.
If you are really a good writer, all your papers should demonstrate your excellent writing skills. If you are able to avoid comma splices in one paper but your next paper is full of them, you probably don't really understand comma splices. Likewise, if your thesis is well supported in one paper, but in the next paper your content is confusing and messy, you need to focus more on how to create an appropriate thesis and support it.