How often do you open your mouth, start talking, and then, after a few effortless sentences escape, hear what you said and realize that it is almost total gibberish? Meaningless. Vacuous and content-free.
I have noticed occasions of that recently. Today I recovered from babbling episode using a technique that rarely works. I kept talking. Normally this only exaggerates the babbling but - I was able to focus and come up with an organization. I made much more sense the second time around. And it was much more succinct.
In extemporaneous speech - talking off the top of your head - you need a plan. Not a complicated one - but a plan nonetheless. You need to know where you are going in order to get there. It is much more interesting for the listener that way.
Think of a joke. The destination is the punch line. If you don't make it to the punch line, the joke is dead.
I reorganized today's verbal diarrhea to follow a timeline. And I knew where the timeline ended-up. I wanted to describe how a program I was testing was working and also tell how I got into the not working state.
"On my machine the website gives an error, even though I tried resetting the config files and that is a different problem than what Steve is having after we used a clean build on his system and we've checked for other differences."
"On my system and Steve's we reset the config files. We did a clean build on Steve's system. We didn't find any differences. We get different website errors on both systems."
So version two isn't scintillating reading, but it was much more effective and communicating what was going on. I simply organized my thoughts to follow the list of things we did, making sure the punch line was "We get different errors on both systems". When the organization came to me I felt that even I understood things better.
So, come up with the punch line first then map out an organization for getting there.