我们换个话题吧!

Let's change the subject.

Let's talk about something else.

Let's talk about something different.

I'd rather talk about something else.

言归正传。

Let's get back to the subject.

Let's get back to the point.

Let's get back on track.

我现在不想谈那件事。

I don't want to talk about it now.

I'd prefer not to talk about it.

Let's talk about it later.

We're playing golf this Sunday, right?

另外我们说说……

To change the subject...

I can't believe it.

好了，玩笑就到此……

Well, all joking aside,...

Ha, ha, that's a good one!

Well, all joking aside, let's get to work.

Well, seriously,...

顺便提一下……

By the way, how is John?

Well,...

Now,...