The Nuns Were Wrong

You can break the rules below because they never really existed. Yup, that's right. Sister Mary Charlotte, who lectured about all of the following non-rules, deserves a ruler slap to the knuckles. Now you can tell your bosses and proofreaders and non-editor friends who try to tell you you've made a mistake that they are wrong. (And you can feel better about the B- you got in fifth grade grammar. Damn those conjugating sentence exercises.)

Splitting infinitives: We’re told to stop the widespread practice of splitting the infinitive, as in the old Star Trek line, “to boldly go where no man has gone before.” But this prohibition is based on the fact that in Latin, it’s impossible to split infinitives – a ridiculous basis for a rule in marvelously flexible English.

Ending a sentence in a preposition: Listen to the wisdom of Winston Churchill:

“This is a rule up with which we should not put.”

Starting a sentence with a conjunction : Charles Allen Lloyd’s 1938 words fairly sum up the situation as it stands even today:

"Next to the groundless notion that it is incorrect to
end an English sentence with a preposition, perhaps the most wide-spread of the
many false beliefs about the use of our language is the equally groundless
notion that it is incorrect to begin one with ‘but’ or ‘and.’ As in the case of
the superstition about the prepositional ending, no textbook supports it, but
apparently about half of our teachers of English go out of their way to handicap
their pupils by inculcating it."

But is a perfectly proper way to open a sentence, but only if the idea it introduces truly contrasts with what precedes. Because is also a perfectly proper way to open a sentence, but only if the dependent clause it introduces is followed by an independent clause (with a subject and verb).