When I did jury service about 8 years ago, we were all taken into one of the court rooms for an explanation of the likely proceedings, shown where the jury sat etc. After returning to the waiting room, which had a cafe attached, about 20 potential jurors were called down for the first case, 11 were chosen, allowing objections from the counsel, and declaring that non of the knew the defendants. The remainder returned to the waiting area. This procedure went on until all the cases that were starting that day had juries selected. Eventually those of us still not selected were told to go home and return the following day. Day 2 followed the same pattern, without the explanations. Those already hearing cases returned to their court rooms when summons, the rest just waited. On day 3 I was chosen to sit on a jury. A couple of times we we asked to leave the court room while some legal arguments were made to the judge. After the judges summing up we were led to a separate jury room to decide on the verdicts. After reaching our final decisions we returned to the court room, where the person chosen as the foreman read them out. The judge deferred sentence until he had received reports from various authorities, therefore we never heard the sentences handed down. We were very lucky as there was supposed to be a case coming up that was going to last for at least 6 weeks, but no one seemed to be called for that case. On about Tuesday of the second week we were told that those not sitting on juries could go home and need not return as no new trials were scheduled to start during the remainder of our period of service.
You probably wont nod off, or need the loo, whilst hearing a case, but take plenty of reading matter as there is a lot of waiting about while waiting to be selected.
Good luck.