You'll probably be on standby for two weeks; jurors from among the same intake are ballotted each time a case comes up, so you might expect one or two cases to decide on in that time. Take a good book to read while you wait. There'll probably be a cheap but reasonable canteen, or you can leave the courts during lunch hour. In court choose a jury foreman (probably someone who's done it before), listen to the evidence, look at the witnesses, try to decide who's telling the truth. You'll have all the time you want to discuss it with your fellow jurors, who will often have sensible and perceptive comments to make. Feel free to speak your mind; also feel free not to say anything if you don't want to, but you'll cast votes, discuss it some more if you're not all agreed, and vote again till you are. The literature will tell you about expenses.