1. Uninstall unused programs.
2. Empty the Recycle Bin.
3. Delete temporary files and folders.
4. Remove large and unnecessary files.
5. Disable System Restore and delete its previous snapshots.
6. Cleanup system errors with a disk utility program.
7. Compress large files to save disk space.
8. Move files to an external drive or cloud storage.
9. Reduce the size of the hibernation file.
10. Use disk cleanup tools like Ccleaner.