on (one's) right side
In the position of being pleasing to one; in one's good favor. The boss is so fickle that it can be hard to stay on his right side. If you want to get on my mom's right side, I suggest getting a bit dressed up for dinner.
right side, on someone's
Also, on someone's good side. In someone's favor. It is often put as get or keep or stay on someone's right side , as in We must get on Bill's right side if we're to get approval of our plans, or Jane had a hard time staying on the good side of her difficult supervisor. The antonym on someone's wrong side, means "in someone's disfavor," as in I got on her wrong side by opening my mouth once too often. Also see wrong side.