I haven't made scripted videos since I deleted my last channel at 3000 subs, but I remember it fondly.
My process has always been 'I'm an absolute god at writing nothing can stop me pale in comparison mortals'.
In reality, it's a little chaotic. My brain can jump from one idea to another in the middle of a paragraph, so my first drafts always end up as word vomit that needs a lot of editing. But that's a very effective first step: Just write. If you have an idea, splay it into fragments across a word doc, and don't stop for a second until you have a grandiose chunk of text to work from. If you just write without trying to criticize yourself, you will often find that you're able to flesh out your ideas very effectively, which will help you put them into something better suited for the spoken word.
Once editing begins, take all of the ideas that you've refined and summarize them effectively. If you don't have any jokes in your videos, you don't have to worry about comedic timing or tone contrast too much. Just focus on getting your ideas out clearly.
When you're coming to a final draft, read it at least three times. In your first read through, try to act as if you're a viewer. Speak out loud and think to yourself: Does this sound OK and make sense? If at any point that feels like a no, take notes on what was wrong so you can make changes accordingly.
Bullet points are only useful if you're naturally a talented speaker, I find. If you have trouble coordinating your speech without strict guidance, they will not help you very much, and you'll come up with very unorganized and poorly constructed dialogue. This is a problem a lot of popular Youtubers face, despite their subscriber count.
Those people telling you "Don't script it, just write bullet points" are one of two things.
Excellent speakers, or people with vapid dialogue.
It's ok to go off script a little while recording. That's just your brain naturally improving upon the written word. Your talent as a speaker will directly correlate with how specific your script needs to get. You'll eventually get a feel for how strict your scripts should be as you write more of them.
Try not to beat yourself up during script writing too, if that's something you tend to do. It's a pretty common issue with all forms of writing.
