Three Cups of Tea

Wiring one-way light point
Wiring is the most common art of electrical installation work. We consider here wiring a light point for 50hz, 230v ac supply. Here are some requirements needed for the wiring: 1.5mm2 [called as 1.5mm squared]; double insulator cable used for live and neutral cables; PVC box to install the light switch; one gang light switch; lamp holder with three terminals; and an install circuit breaker. Earth [E] cables should be 2.5mm2 [called 2.5mm squared] single insulated cable for both industrial and residential use. For residential application 1.0mm2 cross-sectional double insulated copper are commonly used for the phase and neutral.    
Furthermore, to do the preparation, install the switch box at the required position. Then, install the lamp holder where the light should be. Lay ½ PVC conduit from the distribution board to the switch position and from the switch position to the lamp holder position. The conduit can be embedded into the wall structure or laid outside and clip to the wall. Instead of PVC conduits, switch boxes, I prefer that you use a G.I. conduit and switch boxes, because they are being used for industrial type of installation where you need protection for cables from physical damage. In some wooden structured buildings, the cables are installed inside panels without conduits being used. The cables should be color coded correctly for phase [live], neutral and earth.  
After the conduit pipe has gone through, then we now do the wiring, taking note that cable length for the above circuits will be such that voltage drop along the cables will be with the approved limit of 10% of supply voltage. Make sure that the power is shut down to the distribution board. Connect the phase line wire to the outgoing side of a 6A or a 10A maximum from the distribution board, draw the phase wire to the switch box and connect to one terminal. Connect another phase wire to the remaining terminal of the switch and draw it to the lamp holder...