One thing I have noticed that has been consistent in all of my experiences with people with autism is that they know what calms them. For my sister, she knows to bring tracing with her to keep her from having a panic attack during stressful situations. Luckily, her teachers were understanding enough that whenever she had a test she was allowed to take a break and do some tracing for a few minutes. This behavior is common for people who have trouble concentrating or get overwhelmed. My mom, who works with many different disabled kids at my school, says that making a figure 8 with a pencil over and over is one of the techniques she was taught to tell the kids to do if they were in these stressful situations. My sister found this calming technique on her own, along with other activities like knitting, puzzles and listening to music. I know that many people without autism also use these activities to get their mind off of other things, but for her it is more for coping with or avoiding stressful situations that could give her anxiety.