BelovedPet and Ozme had excellent advice.
Ozme is right about enforcing desirable behaviour. This might work a lot better than punishment.

I am not fond of punishment myself. I strongly oppose being treated like a kid, and getting "punished" just feels way too much like a parenting action to me. I donīt like it, and all you will get for something like it will be resentment and an even stronger fight.

For the same reason, I donīt want to be made feel I am "obeying" or "fulfilling tasks". I find I am a lot more eager and comfortable if I am given the choice - if I do something or not is with me.
If I donīt do it, nothing bad happens.
However, if I am allowed to do it of my own free will, his pleasure means worlds to me, and this is likely to motivate me to do it again and again, even if - or especially when? - the action in question I would NEVER want to perform of my own free will if it wasnīt asked.
The more I have to overcome myself in this, the more happy and proud do I feel afterwards.

Regarding "punishments": For the above-stated reasons we donīt do these (giving me pain would not be a punishment as I like it), but feeling his disappointment in me is about the worst punishment I can imagine. It just feels outright horrible, and I do whatever I can to avoid it.

However, this is - at least to me - an extreme way of putting me in my place, and I would caution you not to overdo it.
If your sub is at all like me, the feeling of "I wonīt be able to do it right anyway, ever, no matter how hard I try, heīs always disappointed" will kill all motivation in her, over time...