Depends on the for it takes really you have some breathing exersizes or you can do some half sleep methode or manipulate the "white noice" you get in dark rooms or try to keep an after image of something bright and the modify it into something new all of these require a lil training but it is fun :)

There a number of breathing practices that claim to be a "DMT release." Like you have free drugs inside you already, might as well, right?

Listening to binaural beats or enclosing yourself in an entirely lightless space.