Rules of grammar often have good intentions, but writing is about conveying meaning, and that is a subtle art. It follows that our writing style will be best when we understand the rules, and artfully break them. While this may not be the best strategy in school assignments, there is hardly a published book that never ends sentences with prepositions or splits infinitives or all those other things that people rant about until they have to use them. Regardless of what you may have been taught, there are tons of conflicting sets of rules all created by different people. So I see grammar as a compass guiding my writing, and allow myself to take detours. It’s evolving, co-created by the speakers and writers of a language, not dictated by some mysterious force. So what’s correct is really up to us, the populace, in how we use our language.

1. “If it’s not in the dictionary, it’s not a real word.” The only ways words have ever come into existence is by someone making them up. And unless they can time travel, the people creating dictionaries won’t know about a word until people start using it. Anne Curzan said in her TED talk, “I’m struck, as a teacher, that we tell students to critically question every book they read, every website they visit — except dictionaries.” Dictionaries are created by fellow mortals with limited knowledge who are doing their best to record words as they are used. The fact is that language changes, and dictionaries are updated all the time. So if there’s a word you just made up and used — congrats, it’s real! “People say to me, ‘How do I know if a word is real?’ You know, anybody who’s read a children’s book knows that love makes things real. If you love a word, use it. That makes it real. Being in the dictionary is an arbitrary distinction; it doesn’t make a word any more real than any other way. If you love a word, it becomes real.” — Erin McKean, lexicographer
2. “Don’t use sentence fragments.” A sentence fragment is a group of words punctuated like a sentence but grammatically incomplete. Like this. (For it to be grammatically complete, it needs a subject and a verb, but you needn’t worry about subjects and verbs at the moment.) Almost everyone uses sentence fragments, and they’re often useful for dramatic effect.
3. “Don’t end sentences with prepositions.” This rule only exists because someone noticed that it was a rule in Latin and decided it should be a rule in English too, and everyone went along with it. Well, English is not Latin. “This is the sort of errant pedantry up with which I will not put.” — Winston Churchill (?)
4. “Don’t start them with coordinate conjunctions either.” A coordinate conjunction is a word that relates two equal things (“apples and oranges”), e.g. and, or, but, etc. (not however or which, for example, because they place one phrase in relation to another). Why does this matter? It doesn’t! Pick up any published book, and you’ll probably find a sentence starting with a coordinate conjunction. And if not, here you go.
5. “Don’t split infinitives.” An infinitive, FYI, is the verb form starting with to, as in to be, to have, to floccinaucinihilipilificate. (As far as I know, the last is only a noun, but it doesn’t have to stay that way.) The only reason not to split them is that in Latin, they’re one word so they can’t be split. But English doesn’t have to be like Latin, really! “I have to somehow un-split my infinitive” reads better than the alternatives (even if it’s not true).
6. “Two independent clauses in the same sentence must be separated by a comma and a coordinate conjunction or by a semicolon.” I fell asleep reading that sentence too, and I even like grammar. Basically, an independent clause is a grammatically complete sentence (having a subject and a verb). (Stick with me, because I’m giving you more ways to break this rule!) That means if you have the independent clauses “I was captured by a dragon” and “she was quite reasonable about it,” you would technically write “I was captured by a dragon, but she was quite reasonable about it” or “I was captured by a dragon; she was quite reasonable about it.” (In the latter, you could also use a dash or ellipsis, or put the second half in parentheses, but that’s not the point.) Usually, this is the way to go. But! Omitting the comma (causing a run-on sentence) or the conjunction (causing a comma splice) can be used to much artistic effect, having the words flow elegantly — and a bit rebelliously — along with the smallest pause. My point is, do whatever sounds good (but on purpose).
7. “Hopefully does not mean ‘I hope.’” That is, people claim that it can only mean “in a hopeful way,” as in “The squirrel is watching my food hopefully,” and not “I hope,” as in “Hopefully they won’t steal it.” Really, though, sentence adverbs (words that change the meaning of the whole sentence, like the second hopefully) have existed for a long time, and both hopefullys were in use until someone decided they didn’t like it. (Note that sentence adverbs like thankfully and unfortunately were never questioned.)
8. “‘It’s me’ and ‘than me’ are incorrect.” In the first case, technically, yes, we should be saying “It is I.” Except we shouldn’t, because that’s a really weird way to answer the phone. And in the second, the question is whether than is a preposition or a conjunction. Typically, than introduces another phrase, like “than I am,” so people assume that the “am” was just deleted. But if you call it a preposition (a word like to, for, after, above, from, etc.), there’s no mysterious word being omitted, and the instinct to say me was right all along. That, or it doesn’t really matter because people will understand you anyway.
9. “Listen to the grammar people or else, mwahahaha!” Grammar guidelines are helpful and exist for a reason (mostly good ones), but they’re there to help writers, not to control them. So yes, listen — and think for yourself.