If you wish to operate one light from two separate switch stations - one at each end of a room for instance - you will wire it just as sparky suggests... This is known as 2 way switching - the ability to control a light from two different places.
But you say you have a 2 Gang switch and two lights... suggesting just one light station with two switches and each controlling its own specific light.
You say the switch has 2 Common terminals and 2 L1s and 2 L2s - this is not so... There are TWO switches and Each has its own Com, L1, and L2.
The convention is to place the permanent live wire into the Com terminal and to run the Switched Live off to the light fitting (Ceiling Rose) from either L1 or L2 of the switch - it really doesn't matter which.
The second switch on the 2 gang switch plate is wired similarly but to the other light.
Terminology can be confusing - In the USA your switch will be called 2 Gang Three Way because each switch has three terminals. Each of the switches you have on the switch plate is more properly designated Single Pole (controls one wire) Double Throw (directs it to either of two places) SPDT.
I am not qualified to answer this question but I can read.
Good luck... Take care...
Peccavi, July 2009
