Here's three versions of the sentence that I'm working on. I like them. But they end on at - Jill blew in like a storm cloud, around three thirty, looking for someone to cast thunderbolts at. Around three, Jill blew in like a storm cloud looking for someone to cast thunderbolts at. It was after three when Jill blew in like a storm cloud looking for someone to throw thunderbolts at. The following sentense stars with - Her eyes slitted, taking in the messy foyer
according to the editors with Mirriam-Webster's online website, ending with a preposition is acceptable, so if 'at' works, then let 'er fly.
"Jill blew in like a storm cloud, around three thirty, looking for someone at whom to cast thunderbolts." This version is, I think, more conventionally correct, plus it has the advantage of putting your most powerful word (thunderbolts) in the most powerful position (at the end of the sentence). Let's face it: usually, even if it's technically correct, a preposition at the end of a sentence is pretty weak.
You could rearrange the sentence, as minstrel and JackElliot suggest. Each of the rearrangements does alter the tome and the emphasis of the sentence, though. Or you could let the sentence end with a preposition, if that's what you believe in. The "terminal preposition" rule is one you should obey if you are writing a formal academic essay. But for fiction, there's nothing dire about it. Just consider the alternatives before making a final decision.
Once upon a time ... it was considered a gross faux pas to end a sentence a preposition with. And, as others have already noted, that still holds true in formal writing. HOWEVER, there is more than a little flexibility in fiction writing. Particularly in dialog, btw, since the characters may or may not feel themselves bound by our rules of grammar! But that also holds over to the narrative portions of fiction writing. If you are creating a 'more casual' environment in your writing (as opposed to literary or non-fiction work) you have more than a little leeway in how you choose to present. In other words ... go for it and the hyper-critics be damned!
Truthfully, I hate it when people end sentences with prepositions. I recently purchased a book (non-fiction). On the first page, there was a sentence which ended with a preposition. I returned it. I disagree with Grammar Girl that it is a grammatical myth. I disagree lately common usage seems to trump proper usage. Apparently the rules of democracy went full blown democracy. My professor in college told me that before long, "thru" would replace "through." I promised myself I would pull a Hemingway when that happened. Clearly, I survived this atrocity of grammar. In fiction, I am more forgiving. If you are writing in the first person, grammatical errors (real or imagined) might actually enhance the story. Ultimately, you need to write the story the way the story needs to be written. Write it the way it flows best. Write it the way you want it to be read. And if we ever switch over to "nite," I cannot be held accountable for my actions.
'Nite' and 'thru' are pure laziness, though; some people can't be bothered to learn how to spell, or at least type a word out in full (don't get me started on people who mix up 'then' and 'than' - where the heck has that nonsense come from?!). As for 'prepositions', English allows for them to appear at the end of a sentence in certain cirumstances. It's how the language actually works, regardless of whatever arbitrary grammar rules are in place. It may not be applicable in other languages, but it is in English due to certain features of the language freeing up word order. These sentences still retain their meaning, and can even flow better.
