The first was an American Cream Ale Brewer's Best kit. Of course with those kits they stress all the wrong parts of the process. Seriously, I sanitized my brew pot before I added water to it and put it on the stove. No joke. Beyond that, it all went pretty well, basically to the instructions. I was uber concerned about everything. In the end I made beer. Those kits aren't really designed to make great beer, just ok beer. The single biggest mistake on that first beer was I left it in the primary for only seven days. Now I don't touch the primary (except maybe a fast extract hefe) for at least four weeks. 

The second first brew day was the first time I did all grain. It was a hefeweizen kit I got from Austin Home Brew (who I think is awesome and fully support). I didn't trust the strike water temp calculator so I mashed in too hot. Then I added too much ice and the mash was not hot enough (146) so I added some boiling water. Still too low. More boiling water. Still too low. More boiling water, better or at least acceptable. My temps and OGs were all over the board, I didn't know what I got out of it until it was all in the bucket. It was basically a complete cluster ****. BUT, it made ok beer. (50% eff, but who's counting)

The bottom line for me is every batch is a learning experience. Even if it is a routine brewday, you can take something new away from it. For me, I am constantly trying to improve on my system and process. I try to take good notes so that I can go back and see what I did different (accidental or intentional). 

I enjoy the hobby and I enjoy helping others with the hobby. I love the openness to share knowledge from each other's experience that homebrewer's seem to have.