This could go so many directions, because it is such a huge topic that I am constantly asked about in my work.
Lets start with natural light. Depending on the look and feel you are going for, this can be your ticket. Shooting wide and slow, gives you a beautiful shallow depth of field and that very “Martha Stewart” feel, very lifestyle and editorial looking. I often use several bounce cards, white, black, grey or silver, to throw certain tones of light in the direction I would like. I also cut holes in them and use them in the direction of my light source to throw more or less light in certain areas. I have been accused of liking images to sometimes look spotty. I admit that I may be guilty of this, but it is caused by my love of seeing sun stream through leaves and make the ground sparkle. This is a little different in shooting food, but I feel that it can give great dimension and a natural appearance. I would say that 50% of my work is shot with natural light. Sometimes I use strobes to create the look of natural light when I need more depth in a photo.
Strobes… I think temperature (in a color sense) is very very important. The more a strobe is used, it changes in temperature. We have about 8 heads we use in the studio, generally Photogenic 1250’s, when traveling I often rent ProPhoto systems. It is important to know your equipment and how certain lights act, like kids (haha!) Using several heads that throw different hues of light messes with my head, maybe its just me. Anyways… photography comes down to throwing light at a subject. Mine is usually food, and I use several tools to make light move in the direction I want to show off my subject. With that being said, I think grids are fantastic! Great to control where light is going, and easy adjust the size and power of your light source. I will often clamp a piece of scrim paper with random holes cut in it to give me some depth. For a fill I often back light with a large octobank, with a bounce of some sort opposite. This is a very standard way of lighting food, easy and can be fast. Again, I use different colors of bounce cards to give certain food the effect I would like.The front bounce can easily be replaced by another octobank, or a grid raking light across the front. I almost always have 3-4 lights on a set, grids and banks throwing light in different directions. I think as you shoot more, and your career advances, you get to know lighting like it is your hand. You instantly know how you want to show your subject, and with confidence you create the image you see in your head.
In the end, you have to light how you see an image, not what others are doing. Light to make yourself happy, please the needs of your client and create the image you want to show to the world. Quick note when shooting your lunch with your iphone.. use a white napkin to the front left or right, opposite of the light coming in a window to fill in the front of your food..
Most of this has been about food, so in a quick note about shooting people. I love a very large (6-8 foot) octobank to camera left, a large reflector opposite and a grid from the back. Again, this is what I seem to like. It always changes and different clients always want different looks. Play with lighting and use it as clay to mold what makes you happy!