If you want to know more more about lucid dreaming and astral
projection read Astral Dynamics by Robert Bruse. The book explains
how to use and induce lucid dreams and subtle body projections.
You could try to stimulate a lucid dream automatically by creating a
signal. Like staring at your hands after writing the words "Am I
dreaming?" on them. If you look at your hands and do this several
times a day for weeks, it will become normal for you and you can
stimulate a lucid dream by seeing your hands in your dream with
those words written on them.
Also, it is commonly known that your feet and hands look odd in
some way on the astral plane so that can also be a signal of you
being out of your body. Hope this helps.