Lewis Carroll on how to write a letter

Put the date in full. It is another aggravating thing, when you wish, years afterwards, to arrange a series of letters, to find them dated “Feb. 17,” “Aug. 2,” without any year to guide you as to which comes first. And never, never, dear Madam (N.B. this remark is addressed to ladies only: no man would ever do such a thing), put “Wednesday,” simply, as the date!

“That way madness lies.”

Here is a golden Rule to begin with. Write legibly. The average temper of the human race would be perceptibly sweetened, if everybody obeyed this Rule! A great deal of the bad writing in the world comes simply from writing too quickly.

Don’t repeat yourself. When once you have said your say, fully and clearly, on a certain point, and have failed to convince your friend, drop that subject: to repeat your arguments, all over again, will simply lead to his doing the same; and so you will go on, like a Circulating Decimal. Did you ever know a Circulating Decimal come to an end?

—Lewis Carroll, “Eight or Nine Wise Words about Letter-Writing”