Use that fluff of yours you call a brain.

It is my experience that no one, in the course of conversation, can fail to give themselves away sooner or later. Everyone has an irresistible urge to talk about themselves.

Surfing is like that. You are either vigorously cursing or else you are idiotically pleased with yourself.

Curious things, habits. People themselves never knew they had them. [Witness for the Prosecution, also published in The Hound of Death and Other Stories.]

That is why most great love stories are tragedies.

You've a pretty good nerve," said Ratchett. "Will twenty thousand dollars tempt you?" It will not." If you're holding out for more, you won't get it. I know what a thing's worth to me." I, also M. Ratchett." What's wrong with my proposition?" Poirot rose. "If you will forgive me for being personal - I do not like your face, M. Ratchett," he said.

I've always noticed that if you speak the truth in a rather silly way nobody believes you.