Flash photography is an ever evolving art. It requires mastery of lighting techniques, positioning, and applying the theory and science of light into your photographs. It is a never ending quest to experiment and to keep on trying the best ways to apply flash in a photograph.
I started photography using my pop up flash. Then I bought a speedlite, then I bought a studio light, then I bought another...and another...and then I realized, I really don't need that much lights at all. All I needed to do was position the lights that I get the results that I wanted. I've learned that the fewer the lights, the more dramatic the lighting will be.
I started photographing flowers years ago and I admit it is really addicting, especially if you get your lighting right. So I started doing experiments with my lighting. I was kinda tired of using the usual 2 lights in the front setup . It produced a rather flat, commercial type of lighting. The usual "everything is lit up like crazy lighting". I started to backlight my subject, and also tried lighting them from the sides. Anything just to get away from the usual...and boy did I get results.
When doing this, make your lighting uneven as possible. Or you can setup a ratio between your main light and your fill light or backlight, for example having a 1:1 lighting ratio between the main light and the fill light means that the power of both flashes is even, which would make the lighting flat. If you set up a 2:1 ratio, that will mean that the main light will have twice the power of your fill light. A 4:1 ratio means that your main light will have four times the power of your fill light and so on.
Start with a simple one light in the front and one light on the side approach. Make your front light your main light and the side light your fill, or try reversing it.
Here's what I got for that setup:
Here's the result of backlighting a subject and having the light in the front less powerful than the backlight:
and here's the result of having a light above the subject at 45 degrees, and then having the main light on the right side of the subject:
The trick is to experiment. Be crazy, be creative!