I did this this past weekend during a metal concert I went to with a couple of friends, we had a booth and tried to sell some art. Overall I did about 6 drawings during the show, sold one toward the end of the night.
I have been keeping a small sketch/note book with me and writing my ideas, insight and other such things down. I did this normally but now I am making an effort to be more thorough. It's working out well especially to capture what I think right after I have a dream or when I am up really late.