In order to teleport without having a teammate, when you at least have a small amount of Ki (20% will do). press L while also pressing in the direction of your opponent. This is a good strategy when your opponent is using a "certain-kill" move and you want to do yours in order to attack your opponent from a blindside. Note: This only works for Goku level 3 (he learns it before he fights Cell) and Cell (because he has some of Goku's cells).