The most common problem that I have seen people make with light meters [I worked in camera stores for a few years], is that people would meter the sky or too much of the sky. That will make the photographs under exposed, and so they would lower the ISO [ASA, DIN] to compensate. But that type of compensation just leads to less accurate exposures in general. Aim the light meter down to avoid taking a light reading of the sky instead of taking a light reading of the scene.