Here's what I've figured out in my (relatively few) years lighting the
stage:
Step 1 - Learn "The Rules", in particular the
McCandless Method. The bulk of high school
theatre in my experience has this as a goal. You put a light Here because The Rules say "Though shalt put a light Here and color it thus".
Step 2 - Learn to break The Rules.
Throw the
book out the window or use it to prop up the back of your
console. Sometimes you're happy with the results, sometimes you're not. The goal is to experiment.
Step 3 - Become free to follow The Rules sometimes and break them at other times, often in the very same
light plot.
Me, my first big attempt at breaking the rules was lighting Fiddler at the high school. I saw a photo
in one of my lighting books that I thought really encapsulated my lighting concept, and so I studied what they did to make it look like that, and then adapted that concept into my design. It was great. I didn't use
McCandless fronts; I went with straight warm fronts and then cool 45-deg sides, with tops/backs. It was one of my better designs.
The very next show I lit at the high school was Our Town, and I had what I thought was a neat lighting idea, but I somehow got it in my mind to use the
stock plot and just color it. Worst design I've done. I let The Rules dictate how I lit it, and it wasn't right.
Get a design concept in your head, and then put the lights in the places that let that concept happen. And (probably the best advice I've heard over the years) make every light have a reason for being.
Not that
McCandless's method is good or bad; it is simply one (well-respected) method. I usually don't use it, at least verbatim, but it's about the best you can do with a minimum of fixtures.