It's been awhile, but I thought I'd try to recollect my first experience with shrooms.
My friend L dosed about 30 minutes before me, so I don't know how much she took. I ate a little more than half of an eighth. I don't know what species, but I'd bought them from someone reliable, so I felt safe.
L and I walked down to a little forest area about 20 minutes away. As we walked I became increasingly excited and happy, laughing at everything. By the time we entered the forest I was really feeling it. Following a path for a few minutes we came to a stream where we spend the bulk of the evening. As I was peaking, I was kneeling in the stream, and found the most intense pleasure in tossing pebbles into the water. With the splash only a foot or two from my face, each was like an explosion. I remember thinking it very analogous to orgasm. I also made a game of it, trying not to blink when the water lept up at me.
When I closed my eyes I saw a tube made of geometrical patterns which I was flying through very fast. It was very much like computer animation. L and I had some "deep" discussions, mostly about political, environmental, and socio-economic issues. She also cried a few times, but she later told me that she felt good about crying, that it was something she needed to do. Bad parts? Just a few. I remember feeling guilty because I couldn't feel sympathetic to her, that I was stuck in my very sensory/awe-some trip. A few times I also got a feeling that I was stupid-happy, that I was just smiling at everything and no longer really a thinking creature. These moments passed quickly, and were compensated 1000 fold by the wonderful feelings I experienced.