So one of the most asked questions during my teaching sessions and workshops is this particular one. Well as you all know photography has no rules as to where to start or professionals start @ this settings etc. If you ever have to think about this then you need to come to a stage where muscle memory is used. If you ask me at any given time what my settings for a particular image is my answer would always be "I don't know". After you shoot for a while you tend to just know what needs to be done. Well this is how I used to shoot for someone to understand where to start.
During around 6:00a.m. my ISO is around 400-1000 (preference is 800). Aperture is aroundf2, f2.8 or f4. Shutter speed varies to get my exposure right but it will not be too slow.
During this time my ISO is minimum from 200 - 400, aperture is around f4 to f8 and sometimes f16. The shutter will vary according to my exposure.
Same as early morning.
Now this is what everyone wants to know. Don't we? Well I start @ my widest aperture like f2 or f2.8 sometimes f4 if it's a group. Shutter will be around 160 (minimum flash synch speed). ISO depends on the exposure, sometimes 800 sometimes 3200. I use a Nikon SB910 for these kinda things. If it's outside with no bounce I bounce it off a wall, human, reflector or go external. Never should you use direct flash unless of course there is no other choice.