[adam]

I would say, but I am no professional, to try to use Natural Light as much as you can, my flash can sometimes cause bright spots (the 'core' of the flash) and dark parts on the sides. Just my thought tho

I only use flash when I need it, then you may ask, when do I need it?
I guess it also depends on what you want it to look like

As mentioned above, you can diffuse or bounce the flash to avoid the bright spots, making the lightning more natural