When using 对 (duì) as a preposition, it is used to indicate "to" or "towards" a object or target. As with all prepositions, some care should be taken when using this particle, as usage of 对 doesn't always totally "make sense" or correspond to English at all.
Basic Structure
The structure is basically:
对 + Object + Verb Phrase
Note that you shouldn't be plugging in just any old verb here. Certain verbs are often used with 对, and some even need 对 if you want to add an object (like 感兴趣, explained below).
Examples
他 对 我 笑。
我 要 对 你 负责。
她 对 我 很 客气。
你 为什么 对 我 有 意见 ？
对 is also used in such structures as: 对……来说 ("for... [a person]") ,对...感兴趣 ("to be interested in...") as well as 对···的印象（”the impression on the object“）
对……来说
This essentially means "for... (a person)." It's for making a statement from a certain person's point of view.
The pattern is:
对 + Person + 来说
川菜 对 我 来说 太 辣 了。
对 她 来说 英语 很 容易。
对 我 来说 书法 很 有意思。
