A preposition generally, but not always, goes before its noun or pronoun. One of the undying myths of English grammar is that you may not end a sentence with a preposition. But look at the first example that follows. No one should feel compelled to say, or even write, That is something with which I cannot agree. Just do not use extra prepositions when the meaning is clear without them.

Correct: That is something I cannot agree with.
Correct: Where did you get this?
Incorrect: Where did you get this at?
Correct: How many of you can I depend on?
Correct: Where did he go?
Incorrect: Where did he go to?