You should always meter the scene that you're trying to shoot.
If for some reason, you're unable to, here are some "rule of thumb settings" that go back to film days. It's referred to as "sunny 16"
Set the shutter speed to 1/(your ISO setting or as close as you can. Example, if you're shooting at ISO 200, your shutter is 1/200th
Set aperture to:
f/16 Sunny
f/11 Slight Overcast
f/8 Overcast
f/5.6 Heavy Overcast
f/4 Sunset
It's not perfect but it'll get you close.
Cheers