Let's shake on it.

让我们握手庆贺取得一致。

You strike a hard bargain. Let's shake on that.

你做了笔好生意。让我们为达成共识握手吧。

Let's shake on it. Let's first be friends, okay?

咱们握一下手先从朋友做起，好吗？

And I want it in a cup, with a strawberry shake on the side.

我要装在杯子里，另外来一杯草莓奶昔。

Well, let's shake on that and draw up the details of the contract.

好的，让我们来拟定合同的细节吧。