The Editor's Manual
Free learning resource on English grammar, punctuation, usage, and style.
When to use which: In/into/inside/within, in/during, for/since, on/upon/onto, over/above, over/more than, under/less than, below/beneath/under/underneath, off/of, beside/besides, round/around, to/toward/towards.
It is perfectly acceptable and idiomatic to end a sentence with a preposition. Consider “What are you talking about?” and “This is what I was looking for.”
Prepositions express relations of time (“during the day”), space (“at the market”), and other abstract relations (“the secret of happiness”) between the parts of a sentence. Prepositional phrases comprise a preposition and its object.