Xorg.conf

Section "Device"

   Identifier     "Device0"
   Driver         "nvidia"
   VendorName     "NVIDIA Corporation"
   BoardName      "Quadro 2000M"
   Option         "RenderAccel"       "true"
   Option         "AddARGBGLXVisuals" "true"
   Option         "HWCursor"          "yes"
   Option         "CursorShadow"      "yes"
   Option         "RegistryDwords"    "EnableBrightnessControl=1"
   Option         "UseDisplayDevice"  "DFP-1, DFP-0, CRT-0"

EndSection

The Option "RegistryDwords" "EnableBrightnessControl=1" line allows you to change the brightness of the notebook's LCD via the Fn-HOME and Fn-END key combinations. DFP-0 is detected as the notebook's LCD and since I'm usually connecting this computer to my external LCD, I use Option "UseDisplayDevice" "DFP-1, DFP-0, CRT-0" to set DFP-1 as the primary display.

Not recommended but to allow plugging in a monitor without restarting X, you can add

   Option         "ConnectedMonitor"  "DFP-0, DFP-1, CRT-0"

Section "Screen"

   Identifier     "Screen0"
   Device         "Device0"
   Monitor        "Monitor0"
   DefaultDepth    24
   Option         "TwinView"                  "1"
   Option         "TwinViewOrientation"       "Clone"
   Option         "TwinViewXineramaInfoOrder" "DFP-1"
   Option         "MetaModes" "DFP-0: NULL, DFP-1: nvidia-auto-select +0+0, CRT-0: NULL; DFP-0: 1920x1080 +0+0, DFP-1: NULL, CRT-0: NULL; DFP-0: nvidia-auto-select +0+120, DFP-1: nvidia-auto-select +0+0, CRT-0: NULL;"
   SubSection     "Display"
       Depth       24
   EndSubSection

EndSection

Here I set up the 3 MetaModes: - notebook LCD off, external LCD on, VGA off

- notebook LCD on, external LCD off, VGA off

- notebook LCD on, external LCD on, VGA off

By setting CRT-0: NULL, you can save some battery by turning off the VGA port.