My sons advise was a funny one, or at least it is from his perspective! DO NOT LAUGH AT THE INSTRUCTORS WHEN THEY ARE YELLING AT SOMEONE FOR SOMETHING REALLY STUPID!
My son got IT'd for over an hour in the "hot box"! Then when the instructor finally told him he was done and if he still thought getting yelled at was funny, dont make the comment my son made...."Yes sir, but thanks, that was the best work-out I have had since I got here!"
By the way...the "hot box' is the laundry area room with all the washers and dryers going, making it steamy...
My son being a jock was very much used to being yelled at by coaches and worked very hard for football, basketball, soccer and track..
Yeah, my son didnt really fly under the radar so to speak!