你一定要把面包片切得厚厚的。

Make sure you cut the bread nice and thick.

《牛津词典》

你一定要把网站流量变成钱！

You have to convert that traffic into money.

youdao

当您第一次和女性见面时，你一定要把自己塑造成一个神秘的形象。

When you first meet women, you want to project a mysterious personality.

youdao

It's saying, "Remember, check it out, you want to do this and think about it carefully."

它是指，“记住，一定要好好确认，你需要把它做好，仔细考虑一下。”

Make sure 课堂 - SpeakingMax英语口语达人