Dumbest newbie thing,you did at the drag strip.....
I don't have much for me personally. My first trip to the track was with a friend who had been before. So the most "newbie" thing i've ever done was forget to turn off the traction control(when i was racing my daily driver)
I have seen someone stage with their back wheels, someone that took 10 minutes to stage, and someone that hit the wall because they couldnt control their car when the tires broke loose on the 1-2 shift.