What can make your biography less disjointed than Twain’s?.
Well, probably the first and best thing is to get clear in your head exactly what happened. Twain was inconsistent throughout his book. Usually it was about dates and times, but not always. He even wrote three or for different results for the same event. So do your research before you start writing.
Now you should ask the question “so what?” If you can’t find a reason to put a detail in, don’t. This is how you should get rid of all the stuff that doesn’t really matter. Twain put in quite a few things that seemed to have no point. In one chapter he gave a day-by-day account of them moving into a house. Yet he gave no sense of what it was like during the process or after it was finished.
Once you have all of your events corrected, its time to get them sorted out. Make sure that you organize your modules into a specific order. Generally this should be chronological, but flashbacks (and flashaheads) can make your autobiography more dramatic and can help with issues of relevance. Twain had many things in the wrong order. A lot of things.