did you know that light guns as we-know-them do not work on plasma, lcd, and other modern technology? (although there are some in the works). today's consoles do not have Light Guns... only cross hairs to be compatible with old and new TVs.
there is NO calibration... it could take 10-15 minutes to adjust your actions to have great cosshair control.
it's all relavant to the play... exact location of the sensor bar, your exact point of where you stand... shooting from the hip or from the chest...
i have my sensor bar hotglued to the bottom of my tv, but configured the wii to think it's on top of the tv... this helps me hold my Wii Zapper in a more natural position since my TV is mounted 5' in the air.
what really matters is the sensitivity of the remote and the distance from the senor bar... for links crossbow, i shoot from my rib cage and adjust the sight to move as slow as possible and adjusted the elevation so that my zapper points lower (probably not even at the screen at all!!!)
when you're into the game YOU get a feel of smoothly moving the crosshairs... the only difference i feel when playing is when i'm too close or too far from the sensor bar...
typically i'm 3-4 feet away but have smooth crosshairs at even 6 feet away.
Update from MikeTheAsian: Ghost Squad does have a calibration tool that's just for the Ghost Squad game... you get more points for not using the crosshairs.
I imagine even Ghost Squad will need re-calibrated if you shift your feet much from your original calibration spot.