I'm in the middle of a lighting design for a play. My problem is I have almost enough instruments and dimmers. Or, rather, I have about 2/3 of what I would need for a proper design, but too many resources to be satisfied with a minimal approach.
Lighting for the stage, as the books say, wants to achieve several not always compatible goals. Primary among them is to be able to see the actors. But this is a more subtle goal, in that actually you want to focus on the actors and reveal their forms and expressions (as appropriate). Sticking a bright light in the middle of the room does not achieve this goal particularly well.
The books also go on to give setting the place, the season, the time of day, and the emotional location of the play as well. But here is where I differ. Not to say that these aren't laudable goals. But, particularly in a real-world lighting situation where you struggle with less than infinite resources, the real trick is to find those elements of the play that are either difficult to indicate via costumes and scenery, or that require reinforcement.
And, more often then not, your task is only partly about making a specific statement about a specific place (or mood, or time, or etc); is it as much or more about providing the contrast.
Almost every play has contrasts running through it. Scenes in Verona versus scenes in the Forest of Arden. Scenes at night versus scenes during the day. Scenes in spring versus scenes in winter. Scenes of joy versus scenes of sorrow. Scenes of spectacle versus scenes of intimacy.
So in lighting "Oaklahoma!" your task is partly to provide the wide sweeping expanse of prairie where the wind goes sweeping down the plain and the corn grows as high as an elephant's eye. It is also to clearly differentiate the dark, sordid little shack where Judd lives his furtive life. And as well make it clear that the Dream Ballet is indeed a dream.
For "Under Milk Wood" the task is even more detailed; the exact time of day is essential to every moment of the play. The changing of the hours is an essential detail and an important character, and it is one that is realized largely by lighting.
If you are doing "Peter Pan" with a full complement of theatrical tricks, then there is enough wood panelling, foliage, and naval fittings to clearly differentiate Darling's house, Island, and Hook's Ship from each other. If you are doing it on a bare unit set, or something else more schematic, then lighting may be called to fill in enough of these different environments to draw the audience into them.
So those are the two intermingled tasks (or, rather, the primary two of an entire host of entangled goals) that I tackle first in any lighting design; the overall look (if any) and the way in which that look or looks can be differentiated.
When you have practically no assets to light with, my first fall-back is an area plot and a few specials. You have to light the actors one way or another. And you often want the ability to focus in on only one part of the stage, either for dramatic focus, or because a specific scene is restricted to only part of a unit set. So an area plot buys you a lot of lighting options.
Area plot meaning, basically, divide the acting area into spots that are roughly the size of the beam cast by the typical lighting instrument in your inventory, and cover each of these spots with at least one lighting instrument. Assign dimmers so, at the very least, groups can be brought up individually (such as, all Stage Left, or just the Center...the more dimmers, the more you move towards having individual control of each and every area).
In the very smallest of settings this may just be one front light per area. If you have the inventory, a pair of lights angled to each other, but circuited together. As the number of available dimmers increase, the options you build in increase; the next stage is to split the pairs so you can change their relative levels. If the two sides are hung with different colors, you get a cheap ability to weight the scenes towards one hue or the other.
A more economical option is to add washes; these are large swaths of coverage that include several areas (or even the entire stage) at one sweep, and do so with more saturated colors. In the most budget-stricken situations, par-cans may be all you have for this. The old stalwart the 6" fresnel also works. If you are lucky to have lots of extra ellipsoidals, though, you can add to the options a gobo or pattern "wash" as one of the options. This is a very cheap way of achieving the "now we are in the woods, now we are out of the woods" effect.
The other really big bang for the buck is backlight. Especially if you can double-hang it; give yourself a warm and a cool. With an area plot in a neutral color and two colors of backlight you can get an astounding variety of feels, plus the ability to change the look mid-play for all that helpful differentiation. Add one or two very selective specials and you can light almost any play.
However. Somewhere in my list of goals -- somewhere below "affordable" and "gets finished before opening night" -- is to make lighting that is unique to that production. That isn't a generic solution shoe-horned in. For that, my usual step both in reduced lighting designs and when I have a little more budget to play with is to tackle the area problem in a manner that says more about the specifics of that play.
Instead of hanging a neutral area plot and then trying to add something on top, I work with the basic shape. I remember the set for a Neil Simon that was dominated by tall windows; I integrated window special with backlight so there was always this sense of light coming from the windows into the apartment. For both productions of "Dial M" and "Streetcar" I worked within implicit light sources; the practical desk lamps and so forth of the former, and the harsh revealing sunlight Blanche worked so hard to hide herself from in the latter. And for a "Midsummer" it was the light of a full faerie Moon. Then on top of these very defined sources was general fill in more neutral colors.
Even for something as simple as "Funny Thing Happened on the Way to the Forum" in a standing set, you can take a page from the same classical tradition and light as if the harbor were Stage Left and Rome were Stage Right. In short, a straight McCandless area plot; but one in which you make a conscious choice of the "warm" and "cool" in a way that supports the production's conceits.
In most designs, the "aha" moment for me is when I've managed to draw what I call a Rose; a diagram of the essential lighting directions with quality and color indicated. The Rose may be representational as in the above examples, or rather less so; for a "Snoopy!!!", for instance, I simply double-hung in warm and cool (that is, warm and cool came from both sides, mixing to white; but a vibrant sort of white light that makes colors pop and edges more defined).
I can pretty much hang a show based on just the rose. With the rose and an area plot, I can quickly figure out the necessary inventory. And with the rose and an area plot, I can also document everything I need to know in a couple of magic sheets.
Trouble is, the show I'm doing right now has too few lights to carry out what I need for a proper rose. I can, with some effort, just barely achieve one overall look, but there are several contrasts that I think are important.
Really, this show has everything. There's interior and exterior scenes. Nighttime and daytime (and romantic sunsets, to boot). Summer and winter. Even some subtler ones; artificial -- electric -- light versus natural light leaking into a pre-electrification farmhouse.
And I'm willing to let a lot of these go. Because this might be a unit set, and it might be a laudable goal to help the audience understand when a scene is indoors and when one is outdoors, but the show is about the coming of drought and then the Dust Bowl. And those, and the wide plains of Texas and the merciless sun, are the emotional center of the show. To take the audience through the story properly, I need more than anything else to help them to see the land drying out and the green crops withering, followed by the parched topsoil being raised by the wind into a dark cloud that blots out the sun.
And I have 2/3 of the instruments, circuits, dimmers I need to really tell this. Yet too many resources to be satisfied with not trying to do so anyways.