A simple trick that I learned many years ago from a then, older professional photographer while I was directing a shoot.
Form your hand into an open fist - so you can put it to your eye and see through the other side.
Focus the “hole” on your subject and this immediately shows you what your lighting looks like and can even help with your composition. It cuts out all interference as you are totally focused on your proposed masterpiece!
Easy, and it really works.