do one's homework
Be well prepared, as in Steve had done his homework before the meeting and could answer all of the client's questions. This usage transfers a school assignment to a broader context. [c. 1930]
Words nearby do one's homework
do one good,
do one's best,
do one's bit,
do one's duty,
do one's heart good,
do one's homework,
do one's thing,
do oneself in,
do or die,
do out,
do out of