How do I  use dimmers?

There are lot's of times when you don't want the lights on at full brightness.  An example is a long length of red ropelight I use to show a "do not cross" boundary around the perimeter of the light display.  I dim this ropelight to about 50% to save energy. 

There are several dimming techniques.  You can use the professional stuff called DMX.  This is expensive hardware but can be computer controlled and handle high current demands.  Pro Sound and Stage Lighting is a good place to start.

You might also consider components from Light-O-Rama or Animated Lighting since they are geared more towards the Christmas light enthusiasts of the world.