The concept of leaving the body or having an out of the body experience are erroneous. You cannot leave the body because they body is in you.
What you can do is change your point of view.
We live quite limited by having our viewpoint behind our physical eyes. When you learn to expand it to encompass not only your body but your environment and your different dimensions, that's when you can fully see that the body is in fact inside of you, as is the world.
At this point, you can in fact move your viewpoint and, if needed, create an energy body to explore other realms on Earth as outside of it.
As a young child I used to do a lot of astral travel. It really is a very thin line between our dimension and the astral one.