For the most part I leave two car lengths between me and the car in front of me, however, I do a lot of highway driving. When I come across someone driving slower than 5 under the posted limit, I will usually accelerate until I'm about a 10 feet from their bumper. I than hover my foot over the brake peddle and ride it slightly until I'm a few feet away from them, than back off and repeat the process until I can either pass or they pull over and let me get by.

As for when at a stop light, I usually leave enough space between my car and the car in front of me so I can maneuver somewhat in case some asshole tries to car jack me.

Let me also add, I only tailgate when there aren't cars behind me.