Remove the seat from a Kawasaki vulcan 800?

Unscrew the bolt fastening the seat to the rear fender.

Using the palm of your hand, firmly strike the back of the seat pushing the seat backwards... away from the gas tank.

Essentially what you want to do is jar the seat free, from the bracket it is secured to on the rear fender. In order to do so you need to move the seat towards the back of the fender (toward the taillight)

The best way to do so is by firmly striking the seat with your palm in a motion that is toward the rear fender.