Play it by ear also means to decide what to do at the last minute instead of making detailed plans.

VOA: special.2009.09.13

You weren't making plans.

没有计划。

耶鲁公开课 - 死亡课程节选

You are making plans for a huge surprise celebration.

你正在策划一场大型的惊喜聚会。

Let me 课堂 - SpeakingMax英语口语达人

But he plans to continue making the water filters in the depths of the library.

VOA: special.2009.06.22

This year I'm still making my plans.

VOA: special.2009.12.28