Depending on what browser you use there are different options. I'm assuming from your post that you are probably using the typical Internet Exploder application.
Do the following: Go to tools, select Internet options from the drop down window, in the bottom third (right side) select the "clear history" button. That will do it where it shouldn't autocomplete and no one will be able to tell (without digging) where you've been. You can also delete internet files if you want (where someone may be a bit more ambitious seeing where you've been.
Depending on how worried you are about this you can get a little more extreme, but that should do for now. You can always drop that "show history for X number of days" down to 1 or zero too, but they will always see where you've gone that day.
Cheers
