If I am running and you call me, the complete QSO would be something like:
[ZS1AN] ZS1AN TEST
[ZS1AN] AB0SQ 5NN38
[ZS1AN] TU ZS1AN TEST
So the formal exchange is just the RST and CQ zone, but callsigns will be exchanged during the QSO. Power level and serial number are not required; you just submit your power level with your entry to the contest committee.
See the contesting FAQ on my website www.qsl.net/zs1an