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.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.