Hi,

Astral Projection does require a lot of practice.
It is important to try and maintain a 'passive' attitude when attempting OBEs, as trying to 'think' or 'control' the process too much can often result in failure.
I've found a number of OBEs that I have experienced successfully occurred when I went back to sleep one or two times after waking up. Usually, I find it hard to go back to sleep again, so it happens best when I'm very tired.

There are a number of great books on Astral Projection out there.
You can read a free one online at: http://www.robertpeterson.org/obebook.html