Readers take in dialogue one thought at a time. A frequent mistake of beginners is to combine thoughts, which may be suitable for other forms of writing but not for dialogue. Another mistake is speechifying. Three sentences at a time is tops, yet many beginners write speeches that go on and on.
Sol SteinDialogue, contrary to popular view, is not a recording of actual speech; it is a semblance of speech, an invented language of exchanges that build in tempo or content toward climaxes.
Sol Stein