1.be careful of表示“珍重，保重，注意，关注，留神，当心”，含有警惕、预防之意，后可跟人或物。
Be careful of the traffic.
注意交通安全。
Be careful of yourself! .
保重保重。
Be careful of your health. 保重身体。
Be careful of the man. 当心那人。
They had to be careful of floating chunks of ice.
他们需要当心大块浮冰。
提示
后跟where、how引导的从句或不定式时，要省去of。
Be careful where you take your date.
带约会对象去什么地方，必须要小心。
You must be careful how to spend the money. 你应当注意如何花这笔钱。
They were careful to observe the proprieties.
他们恪守规矩。
He was ever careful to check his scripts.
他一向都认真检查剧本。
She had been careful to sweeten the deal with a rather generous cash payment.
她一直甚为审慎，想要通过支付很多现金促成这笔买卖。
He is careful to show favour to no one.
他谨慎地不偏袒其他人。
Be careful to avoid being subjective and one-sided.
切忌主观片面。
2.be careful with表示“仔细，小心”，“小心处置/对待某事或物，对某事节省/节俭”指提醒某人用心、当心，后跟物作宾语，不可跟人。
Be careful with that ─ it cosplayt a lot of money.
小心别弄坏那东西，它可值钱了。
Please be careful with my glasses.
请当心别打碎我的眼镜。
Be careful with the glasses.
小心这类玻璃杯。
It would force industries to be more careful with natural resources.
这将迫使企业愈加节省资源。
You will have to make a special effort to train your child to be careful with her pocket-money.
你得格外小心培养孩子的节俭意识，零烧钱要省着花。
Do be careful with the experiment you're doing.
在实验中切不可粗枝大叶。
We're newcomers here and must be careful with what we do.
大家新来乍到，得注意我们的一举一动。
be careful with the/your money烧钱精打细算；吝啬、小气
We'll have to be careful with money but that doesn't mean we can't enjoy ourselves.
大家需要精打细算，可也并非说大家就不可以过得快乐。
The waiter was being very careful with the soap so as not to spill it.
服务生拿汤的时候非常小心，怕把汤泼出来。
You must be careful with your homework. 做作业时你需要很用心。（=be careful in doing…）
One cannot be too careful in guarding Party and state secrets.
守旧党和国家的机密，慎之又慎。《汉英大词典》
You cannot be too careful in driving a car.
开车时再如何小心也不为过。
3.be careful for表示“关怀，惦记，挂念”，后可跟人或物作宾语。
She is careful for her mother only. 她只惦记住她的妈妈。
I am always careful for his progress in studies. 我常常关心他学业上的进展。
4.be careful about表示“小心，当心，注意”，“讲究，小心，当心；慎重的，注意...的；对...小心”。
People should be careful about their possessions and not leave them lying around
大家应该小心我们的财物，不要随意乱放。
He really must be careful about thinking aloud. Who knew what he might say?
他的确该注意自己说话不经思索的问题。哪个了解他会说些什么？
Be extra careful about personal hygiene.
要很注意个人卫生。
Be careful about your body language.
注意你的肢体语言。
Be careful about what you say. 说话要小心。
It's the one thing you've got to be careful about. 这件事情务必当心。
be careful about doing sth 慎重、小心、当心做某事
It is important, I think, for everyone to be careful about claiming victory.
我想，每一个人宣布胜利时都要慎重。
I think you should be careful about talking of the rebels as heroes.
我感觉你说话应该小心，不可以把反叛分子当英雄。
be careful有不少同义替换，如take care、look out、be attentive、be cautious，这类短语（句）也可以表达小心、当心、注意的意思。
