When i use FOR and TO

To and for

a)

i) These flowers are for you.

ii) Please give these flowers to Mary.

b)

i) Since it's not my fault why are you blaming me for?

ii) It's his fault so you should address your complaints to him.

c)

i) For your comfort we have acquired a fully air-condintioned bus for this long journey.

ii) To keep you comfortable, a fully air-conditioned bus has been arranged to take you on this long journey.

Hello CJ

I too am troubled with the use of "for" and "to". My problem is which preposition to choose for which adjective.

1. English proficiency is necessary for/to your business success.
2. Energy saving is important for/to the control of CO2 emission.
3. Let's meet at two tomorrow afternoon if it's convenient for/to you.
4. This new analyzer must be useful for/to medical doctors.
5. This new system would be useful for/to our IT business.
6. Those questions must be easy for/to our teachers.

Which preposition is better in the sentences above? If both are OK, is there any difference in the meaning between two usages?

Thank you, CJ. So I'll take it as the rule of thumb to choose "to" for persons and "for" for things with the exception of "easy for persons".