Do allow some lead way on special occasions such as proms
Don't allow them to call half an hour before they are to be in to ask if they can sleep over at a friends. This is generally a red flag saying 'something is up'.
Do set a reasonable time for all involved. If you would like to get some sleep before midnight on a Friday evening, then set the time for 11 pm.
Don't get sucked into the 'what everyone else is allowed to do' conversation.