As with every technology you give to your team everyone has different opinions and conventions. A style guide becomes an indispensible part of your development organisation. Otherwise the ‘tabs vs spaces’ discussion can go on forever.
This also applies to GraphQL. So to help you get started take a look at https://graphql-rules.com/.
Rules and recommendations mentioned here were the results of 3 years' experience of using GraphQL both on the frontend and backend sides. We also include the recommendations and experience of Caleb Meredith (PostGraphQL author, Facebook ex-employee) and Shopify engineers.
This guide is intended to be open source and could change in the future, - the rules may be improved on, changed, or even become outdated. What is written here is a culmination of time and pain suffered from the use of horrible GraphQL-schemas.