This is my talk at GraphQL Finland 2018 that gives both an overview of patterns being used to surface errors that occur during GraphQL query execution, as well as what our (artsy.net) approach is.
You can find the slides on Speaker Deck or as PDF in this repo.
Finally, you can find a recording of the talk here and a blog post version here—where you can also leave comments with your feedback on all of this 🙏