get on (one's) good side
To obtain one's good favor. How can I get on the boss's good side when he's so fickle? If you want to get on my mom's good side, I suggest getting a bit dressed up for dinner.
get on someone's good side
Win someone's approval or support, as in Kate offered to walk the dog in order to get on her aunt's good side. [c. 1930] Also see in good with.