Henry James and Joseph Conrad were good friends, and in mid-career both agreed that in their future books, none of their characters would reply to a question directly, but only comment obliquely—which would add tension.

If you think of speech as action, it will keep you from writing soggy, inert dialogue. Speech as action reminds you that characters talk in fiction because they want to further their own ends.

So that's the foundation for dazzling dialogue. It comes from a character who has an agenda, and is directed toward another character who has an agenda. No matter how small or large the objectives, if they are in conflict the dialogue will work.