What exactly does a Producer DO all day? What does an actress do once she arrives on set? How about an agent?
You could probably find out a good amount of what you are looking for from research. Blogs like Deadline Hollywood Daily. TV Shows like Sunday Morning Shootout. Or even TV Shows like Entourage should give you good insight into the Producer/Actor/Agent level on the industry.
A Documentary like Lost In La Mancha gives you some good insight on the day to day as well. Of course, every one of their days go badly. But the day that the investors show up might be insightful for your kind of thing.
You mentioned Jerry Bruckheimer and what someone of that level probably does on set is show up for an hour, get fawned over, and leave. There was a story on Sunday Morning Shootout told by Jon Favreau about working on the movie 'Rudy' that Peter Guber (co-host of the show, who used to be a very big Producer) showed up to set one day, showed up in the private jet, everyone was waiting for his big grand entrance. He hung around for like an hour and like that he was gone.
What the actors do depends on the set and the actors. Martin Lawrence once stayed in his trailer for an entire day, losing the whole day of filming, because they brought him a grilled cheese with white cheese instead of yellow (he's bipolar). But on the Desperado movies, Robert Rodriquez and Antonio Banderas would chill out and play guitar between takes and things like that.
And it depends on the Producer and the size of film what they are doing. Ray Liotta produced Narc and he'd act in it all day and spend all night on the phone trying to arrange financing to be able to shoot the next day. Or making sure the film made it to the developer. Both Producers and Agents seem to spend a fairly large amount of their time on their cell phones. But some producers are making creative decisions, some are just taking care of practical situations, some are just the money, some are just the actor's girlfriend. What a Producer does can vary greatly.
I don't know where you live, but it may be particularly instructive to work as an unpaid production assistant (better if you could get paid, but unlikely!) on a local independent film. You can check out Craigslist or something in your area and they are always looking for volunteers.
As other people noted, it's mostly waiting. Pretty much the only people who don't spend half their day doing nothing are the cinematography crew and sometimes the director. And yeah, they are seriously serious about the union thing. It helps just not to touch anything =) Food is pretty much always good though.
And similarly what an agent does depends on the client and the agent. Agents spend a lot of their time in their office (well, really they spend a lot of time in restaurants and bars in 'meetings'). But they will be on set if needed or if they need to such up or for certain reasons.
There are some really great books about the film industry and film history, that are filled with great stories and anecdotes, but I don't know if it'll give you the day to day logistics. But Peter Biskind's books - 'Easy Riders, Raging Bulls' (about the 70s) and 'Down and Dirty Pictures' (about the 90s) are greatly insightful into how the industry works. Or the Screenwriting Bible, 'Adventures in the Screen Trade' by William Goldman, also has great insight into the industry. But again, less on that day to day basis.
