Try and write straight English; never using slang except in dialogue and then only when unavoidable. Because all slang goes sour in a short time. I only use swear words, for example, that have lasted at least a thousand years for fear of getting stuff that will be simply timely and then go sour.
Ernest Hemingway Selected Letters 1917-1961 (ed. Simon and Schuster, 2003) - ISBN: 9780743246897