Monitoring Generator Load vs. Engine Running?

Hi. I understand that there are two parameters in a generator:

1. The amount of time it is "running" (i.e. engine is on)

2. The amount of time it is "on load" (i.e. electricity generator engaged)

Basically the times when the generator may be running but not on load is a waste.

What are the parameters (i.e. physical connection points) to monitor to detect each of these conditions? Is there a lamp to tap in to for each condition? Some other signal?