Which is most important in writing dialogue from memory: accuracy, succinctness (brevity and clarity), or liveliness?
This can be a difficult question to answer, since all of these are essential to keeping a reader’s attention. If the conversation is particularly lacking in any of these attributes, the readers will either finish the book with the wrong message, or simply not finish at all. But as to which one is most important, well that mainly depends on the author’s goal.
Succinctness is important to keep the story flowing. If the author becomes too long-winded in his storytelling, people will find it hard to keep reading, even if they enjoy the book. If the dialogue is lacking in clarity, the readers will find it difficult to grasp the meaning and may become frustrated in their attempts to decipher it. Succinctness can protect readers from information overload and act as a lens to help them understand the meaning. But it is not paramount, and most readers will forgive a lack of succinctness if they get a more accurate and exciting story.
Liveliness is very important in any story, even in nonfiction, technical books like autobiographies. If the dialogue does not have an element of excitement, nobody is going to see any reason to read it in the first place–unless the author is a celebrity. A good autobiography will contain plenty of interesting dialogues that draw the readers in and keep them there. But it is most important that all the dialogues advance the plot and help get the main idea across. Focusing all efforts on liveliness will lead to lots of fun but pointless events peppered all over the book with no break in between and no correlation whatsoever. The question is: So what? If it is impossible to answer, the detail had best not be included.
Accuracy is probably the most tricky of the three. If dialogue is completely lacking in accuracy, the purpose is lost. The author may also be criticized for incorrect information. However, an author is not required to get every word right. An author can add or manipulate words, so long as he does so subtly, preserves objective facts, and keeps his point intact. Famous writers who write their autobiographies sometimes create entire conversations from their imaginations. These qualities make the importance of accuracy very difficult to pinpoint once and for all. But there is one exception. If a dialogue is technical in the least, accuracy is key above all else, and should not be compromised to make the dialogue a bit shorter or less boring.
All this said, these three qualities are all very important to any good story. They keep the reader interested, ready for more, and open to the message. They supplement each other and the plot. But as to which is most important, I would say accuracy in most situations. Since when writing an autobiography, the author is mostly focused on events in the real world, he needs to prioritize the truth over excitement.