We must have lunch together sometime. (A vague statement that may lead to lunch plans.) Rachel: Nice to talk to you, Tom. We have to do lunch sometime. Tom: Yes, good to see you. I'll give you a ring. Tom: Can't talk to you now. Catch you later. Mary: We'll have to do lunch sometime. John: Good to see you, Tom. Tom: Right. Let's do lunch sometime. John: Good idea. I'll call you. Mary: Catch you later. Sue: Sure. Let's do lunch. Mary: Okay. Call me. Bye.