First thing worth noting--were you are aware that you can actually go down to a courthouse and watch? Most of the cases are open to the public so you can just go down and sit in and watch the proceedings. I took a criminal law course once, and one of the requirements was to watch how the courts worked. When I was called in for jury duty, there were also people sitting in the audience watching.
I didn't fill out a questionnaire in advance either--I just got a date and reported in on said dates. They had all of us sit in the jury box and each lawyer asked us questions. One case was a stalking and the other was a sexual harassment at a company. A lot of lawyers for the second one. The lawyer for the plaintiff, lawyers for the company, lawyers for the company that owned the company.
I remember the second one as being particularly interesting from the questions side of things. The corporate lawyers got up and went right through the questions (most have already been mentioned here, though they did ask if anyone was a lawyer). We just raised our hands when we could answer a question, and they pointed to us. I remember one of the jurors was really whiny when he got asked why he couldn't serve on the jury. He just didn't want to do it, and it came across in his really lengthy reason. The judge fussed at him (he was a former Marine Corps drill sergeant. Not a good thing).
The plaintiff lawyer got up and my immediate impression was that he didn't know what he was doing. The kinds of questions seemed unfocused and like he wasn't sure what exactly to ask. Since this was a sexual harassment case, that question came up--if we'd known anyone, if it had happened to us, etc. That was one I did answer (when I was serving in the Persian Gulf, my unit had a serious problem with that). They called me up to the bench, with both the plaintiff's lawyer and one of the other lawyers. The judge asked me if I could do the case impartially. The best thing I could tell him was that I would do my best. The plaintiff one wanted me to stay on the case and thought I could be impartial. Nope, said the judge. I was off the case.
Also worth noting--how they do this will vary from state to state. I'm from Los Angeles, and they are notorious for having long cases. My mother served on a jury for thirty days; mine in Virginia was one week. I was told the following about my specific county: A celebrity was arrested. The lawyer from Los Angeles trots in and tells the judge how long he needs for the case: Two weeks to pick a jury, six weeks to present his case. At which point the judge interrupted and told him it was would be two hours to pick the jury and three days to try the case. In our county, it is rare to have a case go two weeks. They try to get them all done in under a week. If you can find someone who knows a lawyer in the area, you can ask him questions about how long the cases run.