Remove temporary files, duplicate files, and other unnecessary data. Use built-in tools like Disk Cleanup (Windows) or third-party apps like CCleaner.
Regularly update your installed software to benefit from performance improvements and security fixes.
For traditional HDDs, defragmenting can improve file access speed. Use the built-in defragmentation tool in Windows. Note that SSDs do not require defragmentation; instead, they benefit from a process called "TRIM," which modern operating systems handle automatically.
Implement strong, unique passwords for all user accounts and enable two-factor authentication where possible.
Adding more RAM can significantly improve your computer's performance, especially if you run memory-intensive applications.