Avoid the elaborate, the pretentious, the coy, and the cute. Do not be tempted by a twenty-dollar word when there is a ten-center handy, ready and able. Anglo-Saxon is a livelier tongue than Latin, so use Anglo-Saxon words. In this, as in so many matters pertaining to style, one's ear must be one's guide: gut is a lustier noun than intestine, but the two words are not interchangeable, because gut is often inappropriate, being too coarse for the context. Never call a stomach a tummy without good reason.
If you admire fancy words, if every sky is beauteous, every blonde curvaceous, every intelligent child prodigious, if you are tickled by discombobulate, you will have a bad time with Reminder 14. What is wrong, you ask, with beauteous? No one knows, for sure. There is nothing wrong, really, with any word — all are good, but some are better than others. A matter of ear, a matter of reading the books that sharpen the ear.
The line between the fancy and the plain, between the atrocious and the felicitous, is sometimes alarmingly fine. The opening phrase of the Gettysburg address is close to the line, at least by our standards today, and Mr. Lincoln, knowingly or unknowingly, was flirting with disaster when he wrote "Four score and seven years ago." The President could have got into his sentence with plain "Eighty-seven" — a saving of two words and less of a strain on the listeners' powers of multiplication. But Lincoln's ear must have told him to go ahead with four score and seven. By doing so, he achieved cadence while skirting the edge of fanciness. Suppose he had blundered over the line and written, "In the year of our Lord seventeen hundred and seventy-six." His speech would have sustained a heavy blow. Or suppose he had settled for "Eighty-seven." In that case he would have got into his introductory sentence too quickly; the timing would have been bad.
The question of ear is vital. Only the writer whose ear is reliable is in a position to use bad grammar deliberately; this writer knows for sure when a colloquialism is better than formal phrasing and is able to sustain the work at a level of good taste. So cock your ear. Years ago, students were warned not to end a sentence with a preposition; time, of course, has softened that rigid decree. Not only is the preposition acceptable at the end, sometimes it is more effective in that spot than anywhere else. "A claw hammer, not an ax, was the tool he murdered her with." This is preferable to "A claw hammer, not an ax, was the tool with which he murdered her." Why? Because it sounds more violent, more like murder. A matter of ear.
And would you write "The worst tennis player around here is I" or "The worst tennis player around here is me"? The first is good grammar, the second is good judgment — although the me might not do in all contexts.
The split infinitive is another trick of rhetoric in which the ear must be quicker than the handbook. Some infinitives seem to improve on being split, just as a stick of round stovewood does. "I cannot bring myself to really like the fellow." The sentence is relaxed, the meaning is clear, the violation is harmless and scarcely perceptible. Put the other way, the sentence becomes stiff, needlessly formal. A matter of ear.
There are times when the ear not only guides us through difficult situations but also saves us from minor or major embarrassments of prose. The ear, for example, must decide when to omit that from a sentence, when to retain it. "She knew she could do it" is preferable to "She knew that she could do it" — simpler and just as clear. But in many cases the that is needed. "He felt that his big nose, which was sunburned, made him look ridiculous." Omit the that and you have "He felt his big nose...."