1. When you turn on the Master Switch, the beacon light will come on alerting anyone on the ramp that your aircraft is about to start its engine and to stay clear.

2.  At night it is obvious that your airplane is manned and about to start up.

While we are on the subject of lights, strobes can be very annoying and disorienting to other pilots while taxiing.  In night operations keep the strobes off until you are ready to take off.  Also, if you are holding short at night waiting for arriving traffic, turn your landing lights and strobes off until the airplane has landed and beyond your position.  It is good practice to turn your taxi lights off while taxiing to the runway if traffic is on short final.  Stop on the taxiway, if you feel you won't be able to safely proceed, until the approaching airplane has landed and is behind you.