Controlling a computer efficiently and writing things down without unnecessary hesitation are rather useful skills, but both may easily be neglected. These notes mostly document my advancements in those, along with musings and observations.
Touch typing is important for efficient and comfortable computer usage. Slow and awkward typing draws one away from keyboard shortcuts and CLI, in a barely noticeable manner, impeding general computer usage. I also remember being lazy to do boring programming bits, and the need to type the code without touch typing was adding more friction. So, I find it to be worth the time investment to learn how to type properly for an active computer user.
The time it takes to reach a comfortable speed is normally about a couple of weeks. There are programs and games (e.g., GNU Typist) that help with practice by detecting typos, measuring the progress, providing texts, and gamifying the process, although one can grab any text and type it as well.
There are more comfortable keyboard layouts than QWERTY, such as Dvorak and Colemak (which I'm using). But non-QWERTY layouts come with minor compatibility issues: you can't type as quickly on others' systems if there's no way to change a layout easily, some software may assume a certain layout and provide key bindings aiming that (most notably, Vim does that; but I use Emacs, which doesn't, except for a few prefix keys, which are preserved in Colemak for that reason).
A handy computer keyboard is nice to use. As with software layouts, hardware ones often come with awkward legacy issues (e.g., staggered keys), but nicer keyboards are available. This is also covered in my computer hardware notes.
I've been taught cursive writing at school, it was illegible and messy, so I was just avoiding handwriting since. Which is not particularly hard with computers around, yet occasionally it is nice or necessary to write things down on paper: usually brief notes, contact information, passwords, or form filling. Possibly maths would be more handy to do on paper too, rather than dealing with LaTeX, live previews, and TikZ (actually my handwritten digits and math notations weren't as messy as words, but perhaps I was avoiding them just by extension).
One day I switched to writing in block letters, and it was legible at once. After a few days of practice and experimentation with letter shapes and sizes, it also became aesthetically satisfactory. "The Path to Dijkstra’s Handwriting" is a nice inspirational article, though my experience differs from that (I wasn't sure if it's worthwhile to practice all the letters, and didn't practice them much, but my starting point was different). It is easy to find additional tips on handwriting improvement, though they seem quite obvious: letter shapes should be easily recognisable as letters they represent, and should be consistent, along with spacing and sizes.
I think block letters are a good choice nowadays, especially if one doesn't have to write longer texts quickly (and in that case, stenography may be more suitable than cursive): they prioritise legibility, which is what matters in most situations.
Apparently people tend to write with fingers, while it's sometimes suggested to write with a whole arm, especially if using a fountain pen or doing calligraphy. It is unnecessary for short and legible notes, and apparently requires quite a bit of practice to be as neat as writing with fingers, if one is already doing the latter.
People prefer different pens (or even pencils). So far I liked a fineliner the most, for its consistent and smooth lines. Gel pens are okay, non-gel (oily) ballpoint pens are more awkward to write with, and fountain pens require a lot of practice to write legibly and not too messily (which may be fun and aesthetically pleasing, but quite impractical). As with computer keyboards, there's quite a few models to choose from and to play with.