There are also states of consciousness that make one very susceptible to experiencing these phenomena.

Various forms of meditation at peak moments can trigger out of body experiences and astral projection.

Also have you ever been physically exhausted and tried to sleep but your mind won't "shut off", until you eventually reach a "waking dream-like state" where you're not quite awake but you're not quite asleep? It's a very delicate and subtle level of consciousness, and you're immediately aware of how fragile this state is, so you can either fight it and become very fearful (and it disappears immediately) or you can embrace it, and then experience what follows.

I've been "visited" a few times by dead relatives when I've been in that state. The most powerful aspect of it for me was the sense of smell as it pertains to the body odour of the individual. As a kid I remember the security of snuggling with a grandparent and baked into that memory was his smell. To experience this in a vision or a semi-dream like state is truly amazing and a little freaky.

I remember the first time it happened, having a conversation with my grandparents, and it felt as real as if they were actually there in the flesh. I recollect the doorbell of our house ringing and going downstairs to answer the door and seeing my grandparents there. They looked vibrant and healthy and exactly the way I remembered them as a kid. As I invited them into the house, I whispered in my grandfather's ear "Have you come to get me?" and he smiled and said "No we're just here for a visit." I then introduced them to my wife and kids, and then said, "wait, you can't go yet. I want to call Mom and tell her you're both here." But by the time I could get to the phone, they were gone, and I suddenly sat up in bed, completely startled with all the hairs on my arms and legs standing on end. This happened about 3 or 4 years ago on Chistmas morning, having gotten up very early with the kids (and having gone to bed late the night before) so that they could open their presents, and then heading back up to bed when they were done. I couldn't get back to sleep but was very physically tired. I tossed and turned for a long time and eventually I fell into this space, and the rest I've described ensued.

Course as soon as it was over I immediately got up and went downstairs and described the whole thing to my wife. I said it didn't feel like a dream because it was too real and the sense of smell really got to me. She suggested I call my best friend who is a psychic and tell him about it. I phoned him, and before I got too far into describing the situation the first thing he asked me was whether I had any sensations of "smell". I said "yup". He said it was probably real, and not a dream. I happened to be talking to my brother a couple of days later, and before I could tell him about my experience, he asked me if anything strange had happened to me in the past few days...and I asked him "why"? He then began describing almost exactly what I'd experienced, and this really freaked us both out!

I think to those that have these types of experiences they are in fact very real, but to try and convince others who've never experienced anything like this, is probably a waste of time. But it only has to happen to you a couple of times, to refute those doubts about the possibility that these things can and do exist.