First of all, feel free to end a sentence with a preposition, despite what your 7th grade English teacher may have told you. If you don’t, certain sentences may sound very strange or overly formal: With whom are you going to the prom? Go ahead and ask who your friend is going to the prom with.
When I taught English as a second language, it soon became apparent that prepositions were the most difficult part of speech for my immigrant students to use correctly, no matter their native language. Do you stand in line or on line? Are you bored of a movie or bored by it? No rule exists to tell you which preposition is correct; most times you just have to memorize them in the situations in which they belong — or for the situations they belong in. (I just ended another sentence with a preposition.)