I’ve tried to cover this before here, but nobody does it quite like Shane.
One of the most important aspects of using the light meter is documenting the results! You always hear about actors on big productions complaining about the long hours they spend in their trailers waiting for the crew to get the ligthting right, and this documentation certainly adds to the wait.
But, at the end of the day, great lighting is a big part of the reason those same actors look like stars on the big screen. And, as a director or DP, you obviously want to produce the best looking frames possible. With repeatability. Don’t skimp on this important aspect of lighting! This is one place where the “Need for Speed” does not apply.
Shane Hurlbut, ASC walks you through lighting a set with a light meter over at Hurlblog: http://www.hurlbutvisuals.com/blog/2013/04/training-your-eye/