Play it by ear

Meaning/Usage: To decide to do something as the situation develops; choosing to deal with a situation as more events unfold.

Explanation: The original meaning is to play music without using a score or music sheet to look at. Just as a musician will play something unplanned without looking at something, this idiom is to do something unplanned depending on the situation.

"I'll have to play it by ear because I don't know how long they want me to work."
"We'll have to play it by ear for next Friday because everything is uncertain."
"Should we plan something for this Saturday or should we play it by ear?"

A: "What are you doing next weekend?"
B: "Nothing. Did you want to do something?"
A: "Yeah, but I might have to give my dad a ride to the train station. I don't know the exact time yet."
B: "Let's play it by ear then. Just call me when you find out for sure."

Other Common Sentences

"I don't have any reservations tonight so let's just wing it."
"We'll just do things as they come along."