If he says, "I suppose I could use some help," he means he fears absolute disaster and needs emergency assistance. Now.
If she says, "That doesn't look good on you," she means that you should burn it in a barrel in your backyard.
If he says, "I think you should watch what you say around Cragmont," he means that Cragmont is an untrustworthy weasel who would backstab his grandmother to get a promotion.
If she says, "Let's do that some day," she means you should never mention the idea again.