I had a slave once but it didn't last too long, about a month and a half. Mine was a Paypig though (financial domination slave).
On cam I would tell him how lucky he is to even be in my presence because he's so worthless.... list random reasons why he was so. And make him do all sorts of silly embarrassing things for your amusement. Dressing up like a woman. Dressing his cock in little costumes. Abuse his genitals with clothespins, rough masturbation etc... Orgasm control and denial, you tell him how to jerk off and then when he's about to cum you make him stop. I also gave him little tasks to do when we were not on cam together. Like make a video of himself in women's panties, singing I'm a little teapot. Or write 200 lines - example i had my pay slave write - "I am a worthless paypig owned by Madame Claes. My life is to serve Madame Claes and give her everything she desires." then they took a picture of it and sent it in to me. Pics of them in degrading positions or outfits holding a piece of paper that says "I am a worthless sissy boy" or "owned by _______" and other phrases are good too.
The financial domination aspect was that he payed double my fetish rate per minute. Also every time he came without my permission on and off cam he would pay a "Cum Tax". Then I also told him to give me a gift of $50 every week on Friday. Which he did, until he disappeared... I think he ran out of money. Which is exactly what appeals to guys who want FinDom, they get off on you emptying their wallets and going broke over you.
Basically you just have to treat them like they aren't worth the dirt on the bottom of your shoes. And that they are privileged just to speak with you and they better do everything you say or they'll never have an interaction with you again. Which if you're a good domme, will terrify them. If they disobey you can punish them through blackmail (ALWAYS HAVE A CONTRACT IF YOU DO BLACKMAIL DOMINATION!), like threatening to tell their family or boss about their dirty secret. Or you can punish them by saying they're not allowed to cum or see you for such&such many days.
How I got the hang of what to say and how to act came from watching A LOT of female domination porn. Never act angry, a good domme never uses their emotions to dominate. A slave is so worthless that they should feel like that their existence doesn't invoke any feelings besides, disgust, pity and pleasure from their displeasure.
This is how I dealt with my slave anyways, I'm sure some more experienced dommes will have some better advice.
