思路分析]
to sb.表示对某人有直接影响比如,食物对某人好或者不好就用to;
for表示从意义、价值等间接角度来说,例如对某人而言是重要的,就用for
[解题过程]
For和to这两个介词,意义丰富,用法复杂.这里仅就它们主要用法进行比较.
1. 表示各种“目的”
1. What do you study English for? 你为什么要学英语?
2. She went to france for holiday. 她到法国度假去了.
3. These books are written for pupils. 这些书是为学生些的.
4. hope for the best, prepare for the worst. 作最好的打算,作最坏的准备.
2． 对于
1．She has a liking for painting. 她爱好绘画 .
2．She had a natural gift for teaching. 她对教学有天赋/
3． 表示赞成同情,用for不用to.
1. Are you for the idea or against it? 你是支持还是反对这个想法?
2. He expresses sympathy for the common people.. 他表现了对普通老百姓的同情.
3. I felt deeply sorry for my friend who was very ill.
4 for表示因为,由于（常有较活译法）
1 Thank you for coming. 谢谢你来.
2. France is famous for its wines. 法国因酒而出名.
5． 当事人对某事的主观看法,对于（某人）,对…来说（多和形容词连用）用介词to,不用for..
He said that money was not important to him.
他说钱对他并不重要.
To her it was rather unusual.
对她来说这是相当不寻常的.
They are cruel to animals. 他们对动物很残忍.
6． for和fit, good, bad, useful, suitable 等形容词连用,表示适宜,适合.
Some training will make them fit for the job.
经过一段训练,他们会胜任这项工作的.
Exercises are good for health.
锻炼有益于健康.
Smoking and drinking are bad for health.
抽烟喝酒对健康有害.
You are not suited for the kind of work you are doing.
7. for表示不定式逻辑上的主语,可以用在主语、表语、状语、定语中.
1． It would be best for you to write to him.
2． The simple thing is for him to resign at once.
3． There was nowhere else for me to go.
4． He opened a door and stood aside for her to pass.
8. 表示前往（某地）去某地,用for不用to
I bought a ticket for Milan.
I start for Shanghai tomorrow. 我明天去上海.
The ship is for Liverpool. 这艘船是开往利物浦的.
9. 表示到达的目的地、终点.用to不用for
The bus will take you to the post office. 公共汽车会把你送到邮局去的.
He saw her to the railway station. 他把她送到火车站.
10． 作为（意思接近as）for可以与to互换.
I’ll keep it for a souvenir. 我将把它留作纪念.
He spoke English so well that I took him for a foreigner.
他英语说的那么好,我还以为他是外国人.
He took her to (or for) wife. 他娶她为妻.
11．for表示交换
1） I bought a bicycle for seven hundred yuan.
我以七百元买了一辆自行车.
2） He is willing to work for nothing.
他愿意义务地工作.
12．表示就…来说,用for
He was tall for his age. 以他的年龄来说他的个子是很高的.
For so young a man he had read widely. 作为这样年轻的人,他书读的是够多了.
13．表示相应、对应,一般for 的前后用同一个名词.
Don’t translate word for word. 不要逐词翻译.
Blood for blood ! 血债血偿.
Eye for eye, tooth for tooth. 以眼还眼,以牙还牙.
To 的此种用法表示贴着,对着.
The two lovers dance cheek to cheek.
这对情侣跳贴面舞.
They stood face to face ( back to back )
他们面对面（背对背）地站着.
14 to 和动词连用,表示“对”,“向”“给”等
Did you mention this to him? 你向他提到这事了吗?
Give my love to your parents. 代我向你父母问好.
http://blog.csdn.net/skyboy1977/archive/2008/11/07/3246771.aspx
实际上是有关介词in和on的区别.介词in和on在表示方位的时候,在用法上有如下区别：
in表示在……中,在……内,例如：
in the village（在村里）
in the street（在街上）
in the fields（在田里）
in the woods（在树林里）
in the wall（在墙里面,例如在墙上打个钉）
on 表示在一个平面上,例如：
on the table（在桌上）
on the lake（在湖面上）
on the wall（在墙上,例如在墙的平面上挂幅画）
再比较：
We swim in the river．（我们在河里游泳）
We have a house on the river．（我们有座房子在河面上）
【in】我是“大姐”,因为我后面所接的都是较长时间.具体用法有：
1． 表示在较长的时间里（如周／月份／季节／年份／世纪等）.如：in a week； in May； in spring／summer／autumn／winter； in 2008； in the 1990’s等.
2． 表示在上午、下午或晚上.如：in the morning／afternoon／evening.
3． in the daytime（在白天） 属于固定搭配,指从日出到日落这一段时间,反义词组是in the night.
4． “in ＋ 一段时间”表示“多久以后／以内”,常与将来时连用.如：in half an hour； in ten minutes； in a few days等.
【on】我是 “二姐”,我后面所接的时间多与日期有关.具体用法有：
1． 表示在具体的某一天（如日期、生日、节日或星期几）.如：on May 4th, 1919； on Monday； on Teachers’ Day； on my birthday； on that day等.
2． 表示某一天的上午、下午或晚上.如：on the morning of July 2； on Sunday afternoon； on a cold winter evening等.
http://zhidao.baidu.com/question/33285646.html?fr=ala0
