As dominants have a specific body language, so do subs. A good sub will know their place, and they will show it in every possible way. To achieve this, you can stand in the way that will make you appear smaller. For example, lowering your shoulders and keeping your head down. Furthermore, you should make eye contact only if you are allowed to do so. Looking at your dom directly in the eyes might look rude and arrogant, which is not a good sub trait. So, keep your eyes on the ground.
As Mistress sound confident and speak loudly, subs should do the opposite. Stay quiet, talk softly, and only speak when your dom asks you a question. Another important aspect is to know where your place is and to do things without your master’s orders. That means things like knowing when to kneel or where to sit, and how to behave.
Sometimes, Mistresses will order their subs to wear collars even in public. That is a great way to remind yourself that you belong to someone and to keep the slave mentality even outside of the bedroom.
The best thing to do is to have training sessions and practice how to be a proper sub and learn a specific skill. Even if you lack some expertise, you can quickly get better to satisfy your master. Maybe your dom wants you to cook for them, and you never managed to do anything but set the kitchen on fire.
The answer is simple — find someone to train you on how to do this properly to fulfill your master’s desire.