FOR and TO

When do you use the preposition to and when do you use for? FOR is used to express doing something on someone's behalf. TO expresses direction.

Examples:

FOR

I hurt my hand and cannot carry my books myself, can you carry them for me?
I also can't use my hand to write. Can you write a letter for me, so I can send it to my mother?

TO

I am up on the ladder painting and I forgot the turpentine, but I don't want to come down to get it. Can you carry the turpentine to me?

Could you send the letter you wrote for me to my mother? Or should I send it to her when I finish painting?

I also can't use my hand to write. Can you write a letter for me, so I can send it to my mother?

I am up on the ladder painting and I forgot the turpentine, but I don't want to come down to get it. Can you carry the turpentine to me?

Could you send the letter you wrote for me to my mother? Or should I send it to her when I finish painting?

Fonte: http://www.englishexperts.net