While working at a clients home, my client Moo, said he would take a video of me explaining my box trick and my technique on cutting in speakers.
It was an impromptu video so excuse its incompleteness. There are additional tips here.
Use a new drywall saw! Mine was old and I got me newer one partially into the video.
If you have insulation this is a great technique because you can catch it all before it falls on the ground.
To mark my hole I use the tip of the drywall saw so that I dont have to balance different tools, it doesnt seem like a huge deal but when your cutting in a bunch of speakers it helps.