After a person has learned how to lucid dream and hopefully crossed the second gate of dreaming by telling an inorganic being to take you to its world, there's another exercise which I personally do and have found it to be rewarding. I'll admit, it wasn't my idea, but came about during a dream with Don Juan where he instructed me to become a tree, which is something I now do in dreaming on a regular basis.
While in that tree form, I look upwards at the sky, and what I see or really hear first, are the stars, as if they are all talking at once. Next, I see strange moving things in the air all around me, like ribbons of living energy, usually a gold color, which combined with all the stars makes for a very cluttered scene. If I focus more on the stars though, the noise goes away and I then see thousands of lines of energy seemingly drawn between cosmic landmarks.
For some reason, the only way I can see those lines in the sky is if I am dreaming myself as a tree, and I've come to understand that they are the only beings in creation who can see that invisible structure of the universe. I'm still trying to find out what benefit to trees there is to perceive this, but it is difficult to analyze in dreaming because viewing those lines is totally mesmerizing.
The other interesting effect is that I get a feeling of being let in on a wonderful secret that creates a bond between me and the trees, which I couldn't even begin to explain. That's why I hope that other dreamers will try this out and maybe give us all some further insights into it.