Astral projection, known by many different names, has been practiced and reported as long ago as the beginnings of modern history. The ancient Egyptians referred to the astral self as "ba", a spirit with the body and wings of a bird and a human head. Through the centuries thousands of people have reported experiences with astral travel. Mystics, scientists, artists, and housewives have successfully learned to launch their astral selves and travel out of their physical bodies at will.
One of the first Westerners who wrote about this process was S. J. Muldoon, whose 1929 book "Projection of the Astral Body" explains how to launch oneself. Make sure you are located somewhere that you won't be disturbed and loosen your clothing. Relax, shut your eyes, and breath deeply. Let tension and worry drain away. Lie on your back on a bed or other flat surface and free your astral self (your consciousness). You travel astrally every nightthrough your dreams, so this process of freeing the astral self is simply letting your mind dream, wander or drift while you are actually awake.
To begin with, you can deliberately induce this split between the astral and the physical bodies at the moment of falling asleep by imagining you are flying or rising in some manner. Teach yourself to remain conscious right up to the moment that you fall asleep. If you can't focus your attention well enough for this, and many people can't, try holding one arm in the air when you go to bed. As you drop off to sleep, the arm will sway and fall toward the bed. That should give youa slight jolt, enough to keep you aware, but not enough to awaken you entirely.
First your astral form disengages and floats a few inches above the physical body. To enable this disengagement, envision your consciousness hanging outside your body, slightly above you about a foot in front of your forehead. Then little by little move the focal point forward until you have focused about six to eight feet from your physical body. Next imagine how pleasant and delightful it would be to lift out of your body and float overhead. Eventually the astral self gradually begins to rise horizontally and move away as it assumes an upright position. The two entities, astral and physical, are attached to one another by a long elastic and flexible cord between the heads, so there is no particular danger of the two parts of your being becoming separated. To return, simply reverse the process. There is a warning necessary here for folks with heart or other serious physical ailments to not attempt this type of travel because the experience for novices can be quite startling.
Always be cautious when you embark in this new fashion, because if you travel to another plane, you might encounter hostile energy or unpleasant experiences. Until you are familiar with the process, particularly for returning to your physical body, stick to visiting all those places you have always wanted to see, right here on the surface of the planet earth.