The idle speed on Toyota is normally controlled by ECU and if you having any problems with it than try cleaning the Throttle Body also check for any intake leak as well...............

Also if its one with Air Condition than live the engine ruining with A/C ON for few min..................

Sir  I also have the same problem, Is any body can help to adjust the RPM of  Toyota Vitz 2011,  Displacement is 990cc.

 Hi
As mentioned here before the idling on most Toyota is been controlled by ECU, if you find the is not right than check and clean the throttle body and idle control valve, replace air filter it if its dirty, check the S/plugs if your S/plugs condition is poor than you will have low idling so, worth changing the S/plugs......................

Your problem may be in the motor mounts. Put a jack under the oil pan and with
engine idling, slightly raise the engine. If the vibration disappears, it's a motor mount
problem.