Once students have mastered the basics of English grammar, it becomes time for you to flip the script. Not all of the rules that you taught them to meticulously follow must be adhered to 100% of the time. The skill comes in knowing when it's okay to throw the rules out the window and when to stick to the script.
Rule #1: You can't end a sentence with a preposition
Typically, writers and speakers should carefully organize their words to avoid ending a sentence with a preposition. However, sometimes not ending a sentence with a preposition is more awkward than breaking the rule. This is particularly true when speaking casually.
For example, "Which box did you put the batteries in?" is okay if you're just asking a friend or relative where the batteries are located.
It is also okay to end a sentence with a preposition when it's part of a longer phrase.
For example, "You're so hard to put up with."
When is it not okay to end a sentence with a preposition? When you're writing an extremely formal piece or when the preposition lacks an object.
For example, "The bird flew up to." The bird flew up to what?
Rule #2: You can't start a sentence with a coordinating conjunction
Conjunctions are used to connect words and ideas in a sentence. Because they are connectors, they need to be connecte to something else. Starting a sentence with a conjunction such as "and" or "but" does not allow for a proper connection to be made. However, sometimes words such as "and" or "but" can make effective sentence starters, particularly when trying to provide evidence.
For example, you may use but as part of an explanation, "But I want to stay here!"
Rule #3: You can't use they as a singular pronoun
They is designed to be plural, but in today's world, the use of they as a singular pronoun has become more accepted. This is especially true in informal speech. If you're not sure whether to use he or she and you don't want a sentence to become cumbersome by repeating "he or she" and "him or her" over and over again, then stick with "they" and "them" as singular pronouns. However, if you're writing a formal piece, figure out the gender or choose the most appropriate singular pronoun and stick with it.
Rule #4: You can't split an infinitive
Star Trek started a trend with its exclamation "to boldly go where no man has gone before." Splitting the infinitive involves putting another word between the two parts of a verb. Typically, the adverb or other word you want to include should come after the verb. Sometimes, however, you need to split an infinitive to emphasize a key point.
For example, "I am going to happily write" and "I am going to write happily" have slightly different meanings.
Although using proper grammar is important, it's okay to push aside the rules on occasion.