If a submissive trusts you, you are in a position of power and influence. That means you are an amateur psychologist, whether you want to be or not. These are some tricks that are fairly safe, which is to say, they might help or fail, but they shouldn't hurt anyone.
Do not try to change a person's personality. Do try to encourage them to be themselves. Suppose someone is too shy, a common problem in submissive men. It is your judgment that they are too shy, and you might very well be right that they will be happier if they are not as shy. But you can't just tell them not to be shy, because they didn't choose to be shy and can't stop. Anyway, if they try to be someone they are not, that is not good. They grow by being themselves and learning, not by trying to be someone else. Accept them as shy, and wait for them to make the small pushes out of it.
If you have an opinion, do not state it as fact. Make it a question. First, you might be wrong. And the person doesn't need someone to argue with. The person can decide. And if you think the person decided wrong, well it would have been worse if you argued. Second, when you have a good insight, the person is more likely to think about it if you ask a question.
How to know what you are feeling. Suppose you are about to say that you feel hurt. You can really check if this feels right. Just compare your feeling to the word hurt. You can tell when there is a good match or there isn't. When there isn't, try to find other descriptions of your feeling, until you find one that fits. The best description of your feeling probably won't be a single word. This trick can also be used trying to understand other people's feelings.
If someone is caught up in what they should do, ask what they want to do. People should always know what they want to do. Then their wants can be considered against their other responsibilities. This is another way of getting the person to be themselves.
A very simple trick is to just repeat back what the person said, in your own words. This is a check that you do understand, and it can help them clarify their thoughts. I mean, you may say the same thing they said, but maybe what they said wasn't exactly right.
As you may have noticed, males and females are not the same. The question is, how should a male submissive be treated differently from a female submissive. This is probably the issue that the School of Caring Domination knows the least about. Some guesses.
Obedience vs. Service. As a rough rule, the male will find obedience erotic. He will probably be a pledger, and he will find it erotic to be held to his pledge and to be given commands. Commands also fit into the typical male work heirarchy. Females, and this is more of a guess, probably do not find commands as erotic. Instead, they are more likely to enjoy service. They are less likely to be pledgers. Instead, given a dominant who cares for them, they will be glad to serve.
One more try at this. For many males, the ideal fantasy is to be completely controlled by his Mistress. Hypnosis is erotic. Training to obey without thinking is erotic. Men, for the most part, probably need enforced obedience. They cannot pick and choose what to obey. For most females, control is not erotic. Women might benefit from picking and choosing.
Father/little girl. One very thoughtful website suggests that most if not all male dominants play the father to the little girl. This is a powerful image, and any male dominant should probably be careful before playing this role too heavily. While males certainly want a strong dominant, it seems unlikely that many of them want a mother or father, or that they really want to be considered the little boy.
Respect. One thoughtful female submissive reports that she is required to play a silly card game with her Master. It seems very unlikely that a male submissive would tell his Mistress that her card game was "silly". Why this difference?
First, if a male thought a card game was silly, he would try to avoid playing it. The female submissive is more likely to be cooperative, because it meets her needs for service. Calling the card game "silly" emphasizes, in an indirect way to both her and her Master, that she is serving.
I think men are more respectful of the female dominant's emotions, while the female submissive perhaps expects the male dominant to be immune to emotional attack.
Dominion. It was suggested that the dominant take over one area of the submissive's life. It is almost for certain that the female dominant should take control of her male submissive's sex life. This is erotic for the male, and it signals the ultimate in control. It is also strategically important. If the female dominant wants to play a serious game of tease and denial, for example, she wants to play when he is horny, not right after he has masturbated. So she needs to know, and the easiest way to know is to control.
Just as a guess, there seems to be little reason to take over the female submissive's sex life. Something like diet might be a good choice.