We all do his when we are sleeping, it's just that we don't remember. So the trick is remembering. You could maybe follow some of the same guidelines you would use for lucid dreaming. like suggesting to yourself before sleep that you WILL remember. A kind of self-hypnosis I suppose. I remember one experience in particular. It happened while I was sleeping I "dreamed" that my spirit was leaving my body via my abdomen at an incredible rate of speed. I kept ending up at the same house.(Somehow I knew how to travel to this house physically even though that wasn't the route that I took). I thought that a friend of my boyfriends had spent his childhood there. When I told my boyfriend about the "dream" he said that his friend had in fact lived there. I could describe the house inside and out including the landscape. Cool. Validation. Good Luck.
This site has some pretty good info on meditation, dream recalling, and astral projection. http://www.spellsandmagic.com/ though it seems like astral projection takes a good amount of practice to accomplish.
Eckankar is a religion that attends to it . one time i did study the Eck book and followed the instructions . all i remember of it is : while reclining comfortably meditatively focus on a point 30degrees above horizontal , command a wave of energy to flow from head to toe , let it pulse one wave following another . fly . actually , i got that wave going . me? i didn't go nowhere . a couple years later i met 2 young women who were Eckankar devotees . seems i was invited to hang out . me? i didn't much care and didn't . these days . i project just fine in love freely without any reguard to being where i not iz . i'd rather just get up and walk to where i dream and go , and i do . it's not neurotic . if'n you got to fly , ya , i spose it's best if you got a group of fliers and a sense of dicipline and ethics . like it could be a positive group activity for prisoners . .