When you set out to produce a show, one of the first things you will need to decide is whether or not the design for your production will be conceptual or fully realized. There are conditions that often lend themselves to one path or the other. Choosing an option that doesn't fit your script may result in you having to fight against the design in order to get your story across.
For our purposes we will be thinking of these elements primarily with regard to set and costumes. Lighting and sound can also be more or less realistic, but sets and costumes are often the areas where a conceptual design is most apparent. In a realistic design, everything is rendered in as much detail as possible, exactly as it would be in the world of the play. In a conceptual design the location and time period are suggested - so instead of the entire castle, you might see a throne and some suspended tapestries, enough to indicate where the scene is taking place.
As a general rule, I tend to be a fan of more conceptual designs. I feel like it gives me more room to play. I feel like it gives the designers more room to play. It can also add another layer with regard to how the play is interpreted. When well thought out and well utilized, conceptual sets and costumes can be incredibly imaginative and fluid. That being said it has to be a good fit for the way your script is structured. Script structure should be the main factor when you're deciding on the design direction. The structure dictates how the story should be told. If a script is laid out in a linear, continuous timeline, you may need to go with a traditional, realistic design. If it uses elements of heightened theatricality, they you may be able to think more outside the box.
For example with a classic comedy, especially farce, you are probably going to be better served by more traditional sets and costumes. Part of the fun in comedy is watching the train wreck. The events are strategically laid out to create a misunderstanding (which is then resolved). Comedy relies on the characters having no awareness of how the plot lines are being tangled while the audience remains completely aware. These plot points usually unfold chronologically in order to make sure that the audience can clearly follow what's going on at all times. (Note: Here we're referring to scripts that are structural comedies, not scripts that are comedic. The Importance of Being Earnest is a structural comedy. Whereas Peter and the Starcatcher is a play with comedic elements.)
Another example of when you might need to go with a more realistic design is when the set (or costumes) functions as an additional character. In these scripts, the design becomes central to the plot. The story is specific to that one location. It's possible that all of the scenes may even take place there. Steel Magnolias, for example, has to happen in a beauty shop. With Clybourne Park, the house is pivotal to the story - you have to see the house as it is in Act I and how it changes in Act II. For Phantom of the Opera, you have to have a mask for the Phantom, otherwise the character (and thus the show) doesn't make sense. These design elements are fundamental to being able to tell the story as it is written. On the flip side, Shakespearean plays, since they tend to be about more general themes and were written to have minimal technical constraints, often do very well with a conceptual design.
If the script is structured in a less linear way, that may allow you to go in a conceptual direction. Perhaps it jumps back and forth between different time periods or it has simultaneous scenes. Perhaps there's a dream sequence. Perhaps you're doing a lot a of double casting and for the overall flow of the piece your actors need to be able to transition instantly on stage from one character to the next. Sometimes the demands of the script necessitates a more conceptual approach. Perhaps there's an element of the script that you're unable to create realistically in a way that's satisfying. War Horse comes to mind as an example where the imaginative integration of puppetry (and other conceptual devices) gave the production substantially more leeway than they would have had had they tried to do a strictly realistic approach.
Plays with numerous locations can work well with conceptual sets because a conceptual set can allow you to quickly transition between those different areas. When you're going from one fully realized location to another, you have to wait for one group of physical objects is taken off and another is brought on. If you're able to simply suggest the location that can be a much less demanding physical change, and thus a faster transition. Come From Away does an exceptional job of this, using a bunch of chairs and small costume pieces to quickly shift between locations and characters - going from bus, to plane, to barroom simply by changing the orientation of the chairs and the way the actors interacted with them.
Going in a conceptual direction may allow you the freedom to create a greater variety of stage pictures. I remember sitting through a production which had chosen to go the more realistic route for a play that took place in two different time periods. The set for the scenes taking place in the present lived stage left, the set for the scenes in the past lived stage right. As a result, the staging became incredibly dull after the first half a dozen scenes because the set pieces severely limited where the actors could be staged.
Often productions end up somewhere in between, with some locations being fully realized and others being suggested. This approach can be a great compromise if it's executed strategically. If you're mixing these two options, you want to be sure either a) the conceptual elements are used often enough to feel like a regular part of the world (not something you defaulted to because you didn't have any other ideas) or b) the conceptual element is used only once, for dramatic effect, in a moment that is meant to be magical.
Depending on the concept, going in a less realistic direction could potentially be a means of staying within your budget. Obviously, if your concept becomes pyrotechnics and Armani suits, that's going to be more expensive, not less. But if the concept allows you to do something significantly simpler or use materials that you already have (or materials someone else is getting rid of) that can be a huge money saver. Again, this won't always be the case, but sometimes it's an option worth considering. The key is to make it look like you chose to design the show the way you did, and avoid making it look like you ran out of money.
The solution that fits your show has to balance what needed and what can be achieved. Embrace the limitations as your unique puzzle and see what the options are.
Thoughts? Questions? Comments? Post them below. The more, the merrier.