Don’t be put off if you haven’t been to a cathedral service before – you’ll be given a service sheet as you go in, so it’s easy to know where to stand or sit or kneel. And you don’t have to believe in God or be a Christian to go to a service – everyone is welcome. The choir usually arrive last and leave first, followed by the priests.
As a general rule the choir will do most of the singing, but if there are hymns then everyone stands up and joins in. People either kneel or sit for the prayers; if you’re worried, just copy what your neighbour does! Sometimes a plate or small bag will be passed around for charitable donations and you can contribute or not, as you wish.