Have you thought about keeping a notebook of things she has asked you to do, and setting some goals each day? Another thing most women like is for their husbands to ask them "What can I help with?" or "What needs to be done?"
Regarding her criticisms of how you do things... a lot of women put importance on things being done "the right way" in the home or with the children, because they see the outcome of those things as a reflection of themselves. You could just be honest with her and let her know that you would like to do a good job, but honestly don't know how... ask her to be patient with you as you are learning. Eventually, as you get stronger, you want to show a stronger, more confident you. Then you can let her know if she would like your help, she should give you some space to do things your way sometimes...