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 in Chinese grammar.

Basic Structure
The structure is basically:
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).


Tā duì wǒ xiào.
他 对 我 笑。
He laughs at me.

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:

Duì wǒ lái shuō shū fǎ hěn yǒu yì si 。
对 我 来说 书法 很 有意思。
I think calligraphy is very interesting.

对……感兴趣 :In English was say "to be interested in something." In Chinese, the pattern is:

wǒ duì shū fǎ ɡǎn xìnɡ qù 。
我 对 书法 感 兴趣。
I am interested in calligraphy.

对······的印象:This basically means "the impression on what you saw or what you know."
The pattern is:

Nǐ men duì dà duō shù měi ɡuó rén de yìn xiànɡ zěn me yànɡ?你们对大多数美国人的印象怎么样?
What's your impression on the majority of Americans?