I think the dream about sitting an exam for which one is ill prepared or not prepared at all is quite a common one. In my case, it's always A level Geography, though heaven alone knows why.
Desperately needing to telephone someone – the police, frequently – and always getting a wrong number is also quite common. In my telephone dream I invariably contact a Chinese takeway while being aware of the sound of a burglar descending or ascending the staircase (depending on which room I am in).
I also talk in my sleep. My favourite is the occasion when, apparently, I sat bolt upright and announced very firmly, "I will not have cats being unpunctual for their meals." Then I lay down again and was quiet.