be good at, be good to, be good for, be good with区别如下：

be good at擅长…
be good with善于与…打交道
be good to对....友善
be good for对....有好处

【例析】
 John is good at maths. And he is good with numbers.
 约翰擅长数学。而且他善于与数字打交道。
 Tom is good at selling. And he is good with people.
 汤姆擅长销售。他善于与人打交道。

 Amy is nice. She is good to me.
艾米友好。她对我友善。
Our English teacher is good to us.
我们的英语老师对我们很好。

Vegetables are good for our health.
蔬菜对我们的健康有好处。
Milk is good for you.
牛奶对你有好处。