1. Play it by ear 见机行事，走着瞧

I'm not prepared for the speech so I have to play it by ear.
我没准备演讲稿，到时只好见机行事了。

释义：本义可不是玩耳朵，而是不看乐谱就演奏，引申为见机行事。

2. Play with fire 自找麻烦，玩火

If you play with fire, you're going to get burned!
玩火必自焚。

疯狂联想：

play with oneself：手淫（粗话），直译是自己玩自己。