The first step is to lower your consciousness to a trance-like state and begin automatic drawing - this is the abstraction part. This is commonly done by meditation. But for me, I listen to repetitive music that overlaps itself - like house or trance music. When I feel like I'm more inside my head than out, then I "feel" where the lines and shapes should be on the paper. This sounds something like "calling the spirits" but it's not; what you are doing is allowing your unconscious dream state to bubble up on the surface - like how it feels when you first wake up. Then as objects appear in your mind's eye from the lines and shapes, then make those images as part of the picture - this is the surrealism part. What's happening here is that your unconscious and conscious are trying to weave the shapes together in the first ways that make sense. In the function our mind in trying to identify things in the world, our personality comes out into the art. To learn more about this identification process see Pareidolia and Hypnogogic Imagery.
The art that I've developed is from the unconscious via automatic drawing. Not only does it give insight into yourself but also insight into how human consciousness affects us. Before I've really understood Jungian psychology, I've seen its representations interveaved throughout my works. One of the most fascinating aspects of this style of art is the fractalization of ideas in one's unconscious and how deeply connected our association of ideas are bound together. I've learned and grown more from this style of art than the most intimate conversations. One key element to propigate this intimacy is to only use pen and no pencils in which you could erase unwanted thoughts. Unwanted thoughts can be as important an informative as wanted thoughts. My unconscious stands naked on the page, no paint to cover it - since it's water color - and no eraser to remove it - since it's in pen. There is a great catharsis of speaking truth as a representative of what human beings are, warts-and-all.