Put Everything on the Same Subject in the Same Place

The most useful advice on writing I've ever received comes from Gil Rogin, who told me that he always uses his best thing in his lead, and his second best thing in his last paragraph; and from Dwight Macdonald, who wrote that the best advice he ever received was to put everything on the same subject in the same place. To these dictums I would add the advice to ask yourself repeatedly: what is this about?