RuneQuest Classic Edition (2e), p. 116:
A new referee should begin simply. Plan to have a couple of beginning players, monsters, and few opportunities for error. Test a few rules at a time, and be prepared to check the book as necessary, and always discuss rules questions with the players – it’s their game, too! Working together, a few trial attempts will instill you with confidence (or convince you that you don’t want to referee).
This was written in 1980. 1980. I love this.