Gentle reminder during setting up for shooting with flash

For knowing whether to adjust cam setting or flash setting during shoot.

Take a sample shot first. 

If you need to light up/dim down the overall photo, change ur ISO/Shutterspeed/Aperture

If you need to light up/dim down only certain parts of your photo, adjust your flash accordingly

Need wider/narrower, move flash closer/nearer

Need stronger power, either set power on flash or move flash closer nearer. But if move flash, take note of the previous point.