Best way to speed up an old Android phone?

My trusty old Android phone has been slowing down a lot lately, and it's getting frustrating to use. I've tried clearing the cache, uninstalling apps I don't use, and even did a factory reset, but it still feels sluggish.

I'm wondering if there's any hidden tricks or apps that can help boost performance without needing to upgrade just yet. Maybe some lightweight launchers or background task managers?

Has anyone managed to breathe new life into their old Android devices? What worked for you, and what should I avoid trying?