Hey Nozturk...I would probably say: 'What do I have to do, to dissuade you from DOING it?' 'What can I do, to dissuade you from DOING it?' You could replace 'doing' with any -ing (gerund) verb form. Maybe someone is about to play some music you don't like: 'What do I have to do, to dissuade you from PLAYING it?' Remember dissuade is normally used when talking about something someone has NOT YET decided to do. i.e.: in the music example above, this would imply the person hasn't yet started playing the music. If they had started to play the music, and you wanted them to stop: 'What do I have to do, to dissuade you from continuing to play that music? Hope that helps :-)

I do not know why no one has told you this, but we would not use dissuade in almost any situation. You specifically asked for recommendations after all. We say: "How can I talk you out of this." "I want to warn you against ...." "I would advise not doing (or trying to...)" "May I recommend not..." "I think you should not..." "I want to discourage you from..." "It would be ill advised too..."

'from doing it' sounds much better that 'from it' 'from it' is unnecessary because the person would already know what you were speaking about. But if you were continuing from a previous conversation you would say What can I do to dissuade you from ...(whatever it is you are trying to talk them out of)? What can I do to dissuade you from doing it? What do I have to do to talk you out of it? How can I talk you out of it? What do I have to do to dissuade you? What can I do to dissuade you? How can I dissuade you?

I'd shorten it. How can I dissuade you from it? How can I dissuade you from doing it? Nice word but it doesn't crop up much in every day usage.