How do I clear the google search, so you can't see previous search preferences?

In your explorer browser click on 'Tools', then 'Options', then
'Content', then 'Auto Complete'. then 'Clear Forms'.

If you just want to clear your previous searches, in the search box
press down and then hold delete whilst the entrie are selected.

If you want to clear your search preferences you need to delete the
google cookie. To delete all cookies got o tools > options > delete
cookies. If you want to delete only the google cookie goto tools /
internet options / settings / view files and search for it there ;)

Perhaps you are talking about when using your Google toolbar, which I
use. Hit the dropdown just to the right of the Google logo on your
Google toolbar and hit Clear Search History.