The Sunny 16 Rule is a great addition to any photographer’s toolbox. Basically it means that when shooting on a sunny day @ISO100 you’d be pretty close if shooting @1/100 and f/16. It is a clever rule because it is very easy to remember. 100 @ 1/100.
Photographer Neil van Niekerk points out that it is pretty easy to complement this rule when trying to overcome the sun with an external strobe. And his method means you can get a great exposure with no metering. The idea is pretty simple: setting your strobe to full power and using the strobe’s GN (Guide Number) to figure out where to place the strobe. This would get a pretty good first exposure.