Do be careful with the experiment you're doing.

在实验中切不可粗心大意。

《新英汉大辞典》

Do be careful, however.

但是一定要小心。

youdao

When crossing the street, do be careful.

过马路时要小心。

youdao

But they do need to be careful not to wound themselves with chainsaws or other pruning tools.

VOA: special.2009.10.06

Let's be careful here; let's do this for Firm 1 and we'll do Firm 2 in a second.

这里要稍微注意一下,我们先写公司1的然后再写公司2的

耶鲁公开课 - 博弈论课程节选

So let me expand on that very slightly, and again we did this last time but I want to do one more time. I have to be careful about how I'm actually implementing a list.

我们之前做过了一次,但还是再做一次吧,我得小心的在列表中执行,例如在这个例子中。

麻省理工公开课 - 计算机科学及编程导论课程节选

But we do have to be careful about how our sensible restraint translates into other languages.

CNN: Does North Korea think U.S. going soft?

However, you do need to be careful that the school you choose is not just a diploma mill.

FORBES: Avoiding the Diploma Mill - How to Choose an Online School

Also, we do have to be careful about speculating on what went on inside a closed-door proceeding from which everyone except the participants, of course, was excluded.

NPR: Rove Concludes Testimony in CIA Leak Case