Five methods are traditionally used to change a man’s perception of his environment: death, drugs, duress, dreams and meditation.
Death
Stories of people staring down on their own body on the operating table or looking through the front windshield after a bad car wreck are very common. Hell, I even had a Navy SOCOM operator tell me the story of how he was stunned from a nearby explosion and saw two jihadis running toward him from around a corner, from a perspective of two stories about his body. While this is a one-way trip for the most part, some ritualized methods exist to explore this that mostly use asphyxiation and resuscitation.
Drugs
Represent a far more common approach to the problem of changing how you look at the world. Traditional societies used a variety of pharmacology from ayahuasca to peyote and more. As a one-time experience prescribed under the guidance of someone who knows what they are doing, it probably doesn’t do too much damage over the long term.
That said, just as many people have good trips as bad and I’ve seen a disturbing trend over the years of people who essentially burned out their meditative potential by having used this methodology. From that standpoint it is a lot like running a turbo on an unprepped motor. Yeah, it will get you the extra performance for a little while, but it usually costs you something over the long term.
Keep in mind, I recommend against this methodology for a whole variety of reasons too involved to get into here.
Duress
Probably the most commonly used methodology of the bunch and a staple of rites of passage everywhere. The Egyptians used to have their acolytes swim across the Nile River when filled with crocodiles. Some South American tribes utilized cliff diving and the Northern Plains tribes had their Sun Dance.
Typically, these events use a combination of exhaustion, fear and pain to change an individual’s view of the world.
A good way to do this on your own is to walk between 50-100 miles in one day. Make sure you are fit, well hydrated and have a plan to get help if things go wrong. By the time you get really dehydrated things get surreal to say the least. Walking on a track tends to induce the state faster but being alone in the wilderness makes the experience deeper.
Dreams
Dream yoga has a long-established history across many cultures with the Tibetans probably having the most developed system for this. Long term these efforts lead to a state closely related to out of body projection.
You will need a notebook and pen to start. The first stage is to say before lying down to sleep, “I will remember my dreams.” Then immediately after waking write down what you remember. After the first week you will have a hard time keeping it to one page.
Next, start pre-planning what you want your dreams to be about. After a while, you will essentially “wake up” during your dreams and have the ability to change things at will. It progresses from there. For vets with bad dreams, even if you go no further with this methodology, this is a great course of action.
Meditation
Meditation is the most repeatable, and controllable, of the bunch. Frankly so many different varieties of this exist that you will need to research what you are most interested in to get a good handle on what you want to do.