You should think twice about employing someone you've never met.

雇用素不相识的人应三思而行。

Recently a campaign against food waste launched online might make you think twice about being so wasteful.

最近网上发起了一项反对浪费食物的活动，这可能会让你重新审视自己的浪费行为。

You might want to think twice about that.

对此，你可能想做三思。

This year, I will think twice about going at all.

今年，我再三考虑要不要去。

Likewise, think twice about what you say before you say it.

这好比说话之前多想两次。