Vaults
I keep things organised with two vaults: one for work-related notes and another for personal/professional notes. For my personal vault, I use Obsidian Sync to keep everything up to date across my laptop and phone. My work vault is synced via iCloud instead, as is GitHub's policy.
The big downside to this separation of concerns is that I can't link between the two vaults. My GitHub project notes are in my work vault while notes about general topics like accessibility live in my personal vault, which I can only access on my own devices.
Themes
Having a different theme in each vault reminds me which one I'm looking at. I use the (unofficial) GitHub theme in my work vault and Minimal in my personal vault. Dark mode in both cases.
Minimal has a companion plugin called Minimal Theme Settings that allows me to customise the theme from the Obsidian settings panel.
The Style Settings plugin also works well with both the Minimal and GitHub themes, giving even more control. This lets me tweak things like overriding Minimal's default heading sizes to make the hierarchy more obvious.
Both themes are compatible with the Hider plugin, which makes it possible to hide certain parts of the Obsidian UI.
Plugins
I try to resist installing too many plugins but there are a handful that I can't live without.
I have tried not to go too far down the rabbit hole with Dataview. Obsidian's roadmap has something called 'dynamic views' which promises to allow us to "create dynamic tables using data stored in note properties". It sounds a lot like Dataview, and I’m inclined to wait for the official solution.