1. Open Finder
2. Click "Go" at the top of screen and choose "Go to Folder" (or click command + shift + G)
3. Copy and Paste ~/Library/Application Support/MobileSync/Backup in the address bar
4. Delete all items in the Backup folder.
5. Empty Trash
1. Go to Downloads Folder in Finder
2. Move files ending in .dmg or .zip to the trash as well as any files you have copied somewhere else, you have duplicates of, or you no longer need.
3. Empty trash.
1. Open applications folder in Finder
2. Look in list for anything that says Install macOS (High Sierra, Maverick, Catalina, etc.) and move to trash.
3. Empty trash