You must always watch out for theft; your money is never safe.
你必须时刻提防偷盗，你的钱从来都不是安全的。

The old man often stands here to watch out for the postman.

老人常常站在这儿等邮递员。

It's up to us, who are the dominant people, to watch out.

我们是占统治地位的人，我们有责任提高警惕。