“Substitute ‘damn’ every time you’re inclined to write ‘very’; your editor will delete it and the writing will be just as it should be.”
“An average English word is four letters and a half. By hard, honest labor I’ve dug all the large words out of my vocabulary and shaved it down till the average is three and a half…. I never write ‘metropolis’ for seven cents, because I can get the same money for ‘city’.
“I never write ‘policeman’, because I can get the same price for ‘cop’…. I never write ‘valetudinarian’ at all, for not even hunger and wretchedness can humble me to the point where I will do a word like that for seven cents; I wouldn’t do it for fifteen.”
“I notice that you use plain, simple language, short words and brief sentences. That is the way to write English – it is the modern way and the best way. Stick to it; don’t let fluff and flowers and verbosity creep in. When you catch an adjective, kill it. No, I don’t mean utterly, but kill most of them – then the rest will be valuable. They weaken when they are close together. They give strength when they are wide apart. An adjective habit, or a wordy, diffuse, flowery habit, once fastened upon a person, is as hard to get.” ~ Letter to D. W. Bowser, 3/20/1880
By the way, you should read his autobiography. It’s hilarious and it’s not chronological, which I suppose makes it more like a memoir.