The idea that you should never, ever end a sentence with a preposition is a myth. Winston Churchill pointed out how silly it sounds to break up a phrasal verb in order to avoid placing the preposition at the end of the sentence.
In general, remove the preposition if it is unnecessary (“Where are you at?” —> “Where are you?”). If the preposition is part of a phrasal verb, it is fine to end the sentence with the preposition. Keep in mind, however, that for academic and some business writing, people may expect you to keep prepositions away from the end of the sentence. If you are writing for school or business, check with a teacher or supervisor OR rephrase your sentence in order to avoid using the preposition at the end of the sentence.
Grammar Girl has a great article on this myth.
This is something I agree with.