You will need a multimeter or one of those electricians screwdrivers that lights up when the blade touches a live wire.
The live supply wire will go to a com terminal and usually be looped with a link wire over to the other com terminal so both of the switches have a live supply to begin with !
One other wire will go to L1 on one of the switches and the other wire will go to L1 on the other switch.The earth wire will go to the back of the metalclad case or brass earth terminal if plastic case.
Chris
November 2006