【俚语】

Use your noodle！
Use your brain!
用脑子想一想！

【例句】
He gave you $10,000? Use your noodle！It’s not that easy!
他给你一万美金？用脑子想想！没那么简单！

Think twice 再三考虑

【例句】
You'd better think twice if you’re gonna invest so much money in a project you know so little about.
投这么多钱到一个你不太了解的项目里，你最好还是三思啊。

Think long and hard 认真思考

【例句】
I’ve been thinking long and hard about going abroad. I just can’t make a decision.
我最近一直都在认真思考要不要出国。我就是没法做决定。

Think sth. over
作决定前认真考虑

【例句】
I don’t think he’s the one for you. You need to think it over.
我感觉他不适合你。你需要认真考虑一下。

Have another think coming
想错了

【例句】
If you think you can walk in here and just demand a raise, you've got another think coming.
如果你感觉就这样走进来，要求加薪的话，那你就想错了。