Maximum Lux: Want to be like a professional retrofitter and measure before/after differences in light output? Do it the right way with the Morimoto MotoMeter--the new standard in aftermarket lighting performance measuring tools.
Location Location: While many measure solely at the hot spot (the most intense point of light at the center of the beam), it's also important to check for glare (light spillage above the cutoff line) and intensity at the edges. Proper dispersion of the beam = better visibility, and isn't that the idea behind all of this?
Easy To Use: The optical eye can be held at the location of choice remotely from the display or hard-mounted to a surface via double-sided tape or heavy duty velcro patches. For consistency, a permanent mount is recommended but not required.