Very good advice on editing from “Mrs Hawkins” in Muriel Spark’s A Far Cry from Kensington:

‘When you are editing copy, Mrs Hawkins, what sort of things do you look for?’ said Howard Send. ‘Exclamation marks and italics used for emphasis,’ I said. ‘And I take them out.’ It was as good an answer as any. ‘Suppose the author was Aldous Huxley or Somerset Maugham?’ he said. I told him that if these were his authors he didn’t need a copy-editor.