A. Go to System Preferences > Spotlight > Privacy. Add any files or folders to this list.

B. Change the folder permissions. Click on the folder in Finder, then choose Get Info from the File menu.
Select the box for Not Available in Spotlight

C. Label the folder with a red tag from the Action pop-up men in the toolbar. Any items marked with a red tag are automatically excluded from Spotlight searches.

D. Control-click the folder and choose Not Available in Spotlight from the Options menu.