如何不动声色改变话题？

By the way, could you do me a favor?

顺便说一下，你能帮我个忙吗?

Before I forget(趁我还没忘)

Before I forget, do you have plans for tomorrow night?

哦，趁我没忘，问下你明天晚上有安排了吗?

That reminds me(…让我想起)

That reminds me of my first dog.

哦，那让我想起我养的第一只狗……blahblahblah

Speaking of(说到/提起…)

Speaking of pets，I really miss my first dog

嗯，说到宠物，我实在很想念我养的第一只狗……

While we are on the subject…(既然谈到这个话题)

While we are on the subject of money, may I ask when you will repay the loan?

既然说到钱的话题，我能知道你什么时候会还这笔贷款呢?