The sunny 16 rule was easy to remember if you observe the light according to the clouds and shadows cast by the sun generally from mid morning to mid afternoon
Bright sun hard edged shadows f/16
Hazy sun soft edged shadows open one stop f/11
Cloudy bright no shadows open another stop f/8
Cloudy dark dim open another stop f/5.6
But at this point hard to judge, might need to meter
Open shade open one stop from f/16
Closed shade open two stops f/11
Sidelight open one stop f/11
Back light open two stops f/8
This is especially useful when working on the run or if the camera metering is questionable. The sun is a constant one can count on.