Are there any best practices?

I don't know if there are for GraphQL in particular. I have my GraphQL implementation as a part of a Ruby app. graphql-ruby has this handy error handling doc: https://github.com/rmosolgo/graphql-ruby/blob/master/guides/... and there's the graphql-errors gem which sort of does this in a generic manner, allowing individual fields to fail without the whole query failing: https://github.com/exAspArk/graphql-errors