The technique was first described by Claude Rifat, a biologist, psychonaut and researcher in his essay "Conscious Dreams and Controlled Hallucinations". Due to the paradigm he adopted, Mr. Rifat eschewed the word "astral projection" and preferred to speak of "conscious dreams" instead. A brief look at his writings, however, reveals that what he called a "conscious dream" was in fact an astral projection.
As to the technique, it is, on surface, simple: choose an object and try to visualize it for half an hour before going to sleep, and then wake up early in the morning (the standard hour given is 4 AM) and resume the exercise for at least half an hour before going back to sleep. Mr. Rifat also tells the practitioner to record his/hers dreams on a regular basis.
I used to do the exercise by the book: in the evening I used to lie awake with my eyes open and focus my attention on the picture of the rose, then the picture of a toothbrush or other mundane objects. Putting the visualized image in rotation helps to mantain the concentration, it is, by the way, mentioned by Mr. Rifat in his essay. Then I used to wake up early in the morning and perform the exercise with my eyes closed.
What you can expect from doing this practice is the increased dream recall and - later on - the ability to cross over into the visualized landscapes. The results, I must admit, are quite dramatic, and doing the exercise with eyes open - even though much more powerful than practicing it with one's eyes closed - can bring you into attention of larvae and other denizens of the World Next Door. Be warned!
As to the experiences I had with this technique, I'm going to post them into a appropriate sub-forum.