Do your research
You need to have done research on how you want to be dominated. Is it bondage that you like or role playing? You need to decide what domination means to you and take it up with him.
When you tell him how you want to be handled, put on your sexy voice and tell him exactly what you want, with some demonstrations of course.
You don’t want to take it overboard and have one of you end up hurt emotionally or physically. Coming up with a safe word is perfect for knowing when you’re overstepping the mark. If you’re using objects for spanking maybe draw the line on anything that leaves a mark.
Make the right noise
Your sighs and moans will show him how turned on you are. Even if he wasn’t into the kinky stuff – hearing you take pleasure from this will get him hooked. It’s good to also let him know how well he’s doing in between your moans, just as an ego booster.
This might scare the both of you at first if it’s not your usual thing. Tell him how bad you’ve been lately and need to be punished. He must be commanding and aggressive in his dirty talk, by telling you what he’s going to do as opposed to asking how you want to be punished.