When being tailgated, you tap your brakes frantically in morse code type fashion. You tap them hard enough for the lights to light up, but not to actually slow down. It'll confuse the tailgater and they will back off. If they continue to tailgate, continue to freak out on the brakes. A skilled driver will be able to brake freak with the left foot while still using the right foot to maintain speed.
The other day someone was tailgating me, so I did a brake freakout and they had no choice but to slow down.