If you are interested in coin collecting, the first thing to do is to find a rare coin.

如果你对硬币收集感兴趣，首先要做的就是找到一枚稀有的硬币。

youdao

The first thing I did was to get completely detoxified.

我做的第一件事是彻底脱瘾。

《柯林斯英汉双解大词典》

Because I was going to say, that's the first thing you need to do and without that we can't go ahead.

因为我要说的是，这是你需要做的第一件事；而且没有（完成）这件事的话，我们无法继续下去。

youdao

It was huge! The first thing that came to my mind was actually that's a lot of food!"

VOA: special.2009.11.23

Your first thing is responsibility to fulfill your rights to your people, to your culture, to your family, to your government.

你的首要任务是履行义务而不是行使权利,对人民，对文化圈，对家庭，对政府都是如此。

普林斯顿公开课 - 人性课程节选

Let's take the first thing first, the radical theology. I'm only able to talk about a small component of Milton's theological daring here.

先来谈激进的神学观点，在这里我只能,谈及弥尔顿神学上的大胆突破的一个小小的组成部分。

耶鲁公开课 - 弥尔顿课程节选

And this goes back to the first thing I said at the briefing.

WHITEHOUSE: Press Briefing

Luckily, the far-sighted BBC South Africa Bureau Chief had already made reservations on a flight to Johannesburg first thing the next morning.

BBC: How I left Zimbabwe

The Stories feature, though in its infancy, has the potential to become the first thing people skip to when they open Twitter.com.

WSJ: A Few New Reasons to Reunite With Twitter.com