One reasonable way might be to incorporate multiple small gestures of your control over him. Just a few ideas that Mistress Jenna incorporated in my training:
- Assign him a new slave name and require that he addresses you with a designated dominance title/honorific that you like.
- If he forgets to properly address you, or is otherwise rude or disrespectful; police his speech and discipline as needed. Give writing assignments as punishment and/or have him gagged for a while. Make it known that those his freedom to speak can be revoked at any time.
- Require him to keep a journal/diary of his training and have him share it with you.
- Physically control his body. Chastity is a great start ;D although there are many other wonderful methods out there. Place him in bondage whenever you want (Rom-com movie marathon while he's bound and gagged so he can't whine about it? Giving him a time out? The possibilities are endless...)
- Make him wear panties. Even better if you have him buy them in person at a place like Victoria's Secret.
- Butt plugs are a wonderful addition to a submissive's wardrobe! Make him wear one whenever, wherever, and for however long you fancy. For me, accepting a butt plug became a gesture of surrendering complete control to my Mistress. After all, when I've allowed someone to access a very intimate part of the body, let alone Her inserting something there, and then being required to keep it there until told otherwise, is arguably a very submissive gesture. When someone else owns your ass, what's left that you really have control of anyway?
- If/when you feel that it's the right time, get him a collar. Make it known beforehand that if he wants to be collared, he'll have to earn it. "Consideration/Training" collars can be used as intermediate steps en route to the formal slave/ownership collar.
- Establish codewords or gestures that can be used anywhere to trigger or convey an aspect of the relationship and discretely bring out the D/s dynamic anywhere.
- Write up a contract or some form of agreement formally outlining each other's roles together. Let it be a living document and tweak it as needed over time.
- Assign him any and all errands and chores. Make him repeat tasks if and when your expectations have not been met.
Honestly, the possibilities are endless. Try whatever sounds good to you and enjoy the process!