I've just realised that I'm wrong, we went to the crown court (but it possibly had magistrates cases, I don't recall - this was over 3 years ago). Either way, we just turned up and walked in.
In terms of 'interest', it's going to depend on which cases are being heard. We went and had some being dismissed in 5 minutes (guilty plea - date set for sentencing; not guilty plea - date set for trial), so you can end up in some 'duds'.
You obviously want a trial, but I'm not sure you can find out what stage a case is at - the courts wil llist the cases, but I don't think they tell you what is actually happening - though if a court room is booked for fewer cases then you could assume one of those is a trial.
We ended up in a trial for a historical case of sexual abuse - which we were surprised at, as the court room next to us had reporting restrictions on, so we wondered why this one didn't.