When I was a kid I would always use the time to daydream. There was a time where I was looking forward to go to a meeting because I can finally think about stuff without having to do something else in that time (like homework or study). When I was little of course I hated going to the meeting and I got so often beaten in the back room because I was misbehaving.
I was not even allowed to have a pen and paper like some other kids, because I should concentrate on the talks. So it was either developing good daydream skills or got beaten. Thats another point, I still argue to this day with my father (happens to be an elder) that they should have special classes during the meeting (like the do in the 'worldly' churches) for little ones.
As I got older I had to find new thinks, so I started counting stuff. I counted how many lamps our hall had, I counted chairs (even though I knew how many there were) I counted how many bros/sis where wearing something blue/red/green and so on. I was never allowed to sit next to a friend only next to my parents so you have develop stuff which keeps you sane.
When I was old enough to do microphone service or handle the sound and got appointed to do it, i LOVED it. Because finally I could keep busy without having to look left/right even someone else is watching me.
Still to this day I often volunteer for the microphone service so during paragraph reading I can be in standing in the back and play with my tablet or answering emails without someone else looking on my screen. I once finished a personal project on my tablet during a meeting that way.
I often see elders wandering around during a meeting, I can imagine that they are bored as well. Then there is this elder, he never sits with his wife just wandering around the hall pretending to do stuff or sometimes he will walk to his other elder buddies and always gives them a note DURING the meeting, something very important whe he couldnt do BEFORE the meeting starts. He doe that until his studies arrive (sometimes they are 30 or 40 minutes late) and then he will sit with them in the back. Not sure why he does that, probably to count the time while at the same time loaths to sit next to his wife haha.