Might I suggest watching Twelve Angry Men? Apart from that... I have no idea whatsoever.

First of all, stay cool. No one else on the jury is necessarily going to be a great debater, either. You just have to decide whether the evidence before you is convincing. The result will mean nothing to any of you personally, so don't get too wrapped up in your point of view and just look objectively at what you've got.

Second, the vast majority of criminal cases won't involve rape or murder, but if it is one, you'll find out at jury selection. Then re-read what's above.

every time I've ever got called in for jury duty the case has already been dismissed by the time the jurors show up. Might happen to you too.

If not, there's still a good chance they won't select you; depends on what the attorneys are looking for. if you are selected, the number of small, petty crimes greatly outnumbers the big, violent ones. From what I've heard from people who have served on juries, it's more likely you're just going to be bored than anything else if you do get selected.

I'd just go with it and see what happens. Chances are good it won't end up like you fear it might.