someone said above that you could plot a route on a chart and go through all the stages of the flight (taxi, take off, en route, possible diversion, possible mayday/mayday relay). Remember to keep quiet if a mayday is in progress (I did fortunately!).
Remember the examiner is not there to catch you out or even to make sure you know everythng down to a T. A few small minor mistakes are allowable I think, just make sure you know the items requiring read back (qfe, qnh, take off & landing clearances, circuit joining instructions etc). Also appropriate use of "WILCO" (will comply) and "ROGER" last transmission received) would be a bonus. E.g. TWR:"G-OP report right base". G-OP:"Wilco, G-OP".