Prepositions

    Sometimes I don't know which preposition is right.
    I was writing a comment to a certain film, and I wanted to write my feeling sympathy.
    I realized I didn't know which preposition was suited to that situation.
    I wrote I felt sympathy for him, but one second later, I thought it might be right to write "to" instead of "for", and then, I'm completely confused it would be better to use "with".
    I should ask someone whom speak English as their mother tongue.