I have astral projected many times and have practiced lucid dreaming for ten years now.
This is what I know based on my experience:
When we go to sleep, our astral body seperates from the physical all the time, weather you are conscious of it or not.
A Lucid dream is being aware of all the subconscious projections as you are in the astral.
Now, when you can be clear of the subconscious projections, that is when you see what is really there.(a clear astral experience)
To become clear of the subconscious projections, it is good to practice to NOT fall into day dreams as you are awake, but be as aware as possible of your physical surrounds in each moment to moment as you are awake.
One time I was very aware in the astral and was perceiving what was actually there, and I saw my brother walking along looking drunk. He was mumbling and talking outloud to his friends who were not there... I knew that he and I were in the Astral, the difference was that I was clear, but he was involved in his dream (his subconscious projections).
It is just like how you can be awake at work and then you see you co-worker "staring off into space." You say their name and they do not respond. You say thier name again, and again they do not respon. then you wave your hand infront of their face and they jolt a bit, and it is funny, they admit they were Day dreaming.
This is how it is in the Astral: you can be clear and then start dreaming.
like you were clearly flying in your room and then sarted to dream that you could make the clock float.
I hope this made some sense to you!
Keep up with investigating on your own. there is so much to explore and find out for ourselves!

Sheena