Wow, I'm surprised the OP writer didn't get bashed and insulted for writing on this kind of subject on smashboards. Anyway, I've practiced bit of astral projection and I've actually gotten pretty close a couple of times, there are several techniques that you can you to separate your astral body (or whatever you want to call it) from your physical body. What happens when you implement these techniques is that you start to feel vibrations (like warm ones) all over your body and your body starts going numb, this is accompanied often with weird sounds.
There are several methods of trying to astral project:
1. From awake
-This is the hardest method, it's easy to relax your body but it's not so easy to relax your mind without falling asleep
2. From a lucid dream
-If you see a lot of lucid dreams this is a fairly easy way to try to astral project, what you need to do is choose a technique and start implementing it in a dream, I've tried mainly these two techniques:
A. Levitation
What I do in a dream is that I go lying on my back on the floor (or whatever) and then start to levitate, you start to feel the vibrations very soon after you start doing this. The issue is that it's hard to wake up from the dream so what has happened to me is that I raise up in a dream higher and higher but I don't wake up. I once had a dream where I tried this method up to 10 times, as I rose higher I realized that I wasn't actually astral projecting, then I woke up in a dream and repeated the process, this happened like ten times to a point where I was actually frustrated in my dream.
B. Rolling over to a side
Try this method in your dream and you will probably get tricked by your consciousness lol. EVERY TIME I've tried this method I the dream changes so that I see myself falling off the bed thinking I am awake even when I am really not, this is when I stop trying this method. Normally your body is paralyzed when you sleep so there shouldn't be any danger of this.
I've had several dreams where I actually am in my room floating in the air but they have been just dreams.
3. Via sleep paralysis
If you don't know what sleep paralysis is google it.
In a sleep paralysis you are in a perfect state to project because your body is paralyzed & relaxed but you are consciously awake. The tricky thing is that sleep paralysis doesn't usually last very long so you have to use the techniques. Also if you have hallucinations & fear attacks they hinder the process, I once felt like I rose above my body but I heard a devilish voice and got so scared I had to stop the process.
The good thing is that if you get sleep paralysis often (that is when you mess up your sleeping pattern) you learn how to control the fear attacks and the state starts actually feel pretty pleasant.
4. Waking up (best method)
I haven't actually tried this method seriously but it's said to be the most effective, it takes some practice tho. When you wake up you must not open your eyes nor move, then you can implement separation techniques straight away because your body is completely relaxed till you move it.
There are several good pdfs on the internet on the subject, the best one is called "School of astral projection" by Michael Raduga, you can download it here:
http://dl.dropbox.com/u/26534647/1 - School of Astral Projection by Michael Raduga.pdf
One last thing I have to say about this subject is that when you actually astral project you KNOW it.