The second best thing you can do for a Win10 computer is turn off whatever unnecessary services it's decided it needs to run in the background always. Some services it does need, but others are useless. Here's an article that goes into step by steps.
10AppsManager lets you uninstall bloatware. Winaero Tweaker lets you disable crap like Cortana/Copilot, ads, telemetry, internet search results when you search from the taskbar, and all kinds of other stuff, plus it gives you lots of other little options that are just nice to have (like, it can restore the old MS Paint program in place of Paint 3D). Both are totally free.
Oh, and check your startup programs in the Task Manager tab to make sure your computer isn't automatically starting eight million programs every time it boots. But I think people mostly know about that. (Unless this is me going "they only know one or two feldspars... and quartz of course.")
The first best thing you can do for a Windows computer is install Linux Mint. But some of us do need a few pesky Windows-specific programs. Bleh. Still, if you're up for a project, you can have both (and it's awesome). Here's an article about setting up a dual boot Windows/Mint system.