Let me tell you my story. 我跟你说说我的故事吧。

　　Let me tell you about my plan to open a restaurant. 我来跟你说说开饭店的计划吧。

　　Let me tell you something. Your girlfriend isn't cute. 我有话要说，你的女朋友长得不好看。

　　I have to tell you something. It's about your ex-wife. 我得告诉你一些事情。是关于你前妻的。

　　I heard you climbed Mount Everest.  我听说你爬珠穆朗玛峰了。

　　Let me tell you, it was really difficult.  我告诉你，这可相当不容易啊。