Out of the many things that actor’s struggle with, structuring a role tops the list. This is primarily because they are unclear about “how” to structure.
In the context of rehearsing a role there are two sources of what I call “given structure”. The writer provides the words and the director provides, blocking, business, concept and overall interpretation of the script. However, these given structures are insufficient to fully develop the role. It’s the actor’s job to create additional structures that really bring the character to life.
A good example is the moment before you enter the performance space. Quite often the script is mute regarding the “moment before” and the director seldom comments on it. It is up to the actor to provide a structural stimulus that takes them into an experiential environment and supports their entrance. That stimulus could be a mental image, an emotional response or even a “physical feel”.
This same example would apply to the moment before you say the first line of your monologue. As you move through the monologue you may need to evoke structures that reflect changes in thought, emotional response and your perception of the person that you’re speaking to (in the context of the monologue).
In general you need less structure to develop a monologue than to fully develop a role in a show. Much of the structuring in a show accommodates the needs of the physical space and staging of the action. In a monologue audition you are in open space and most of the kind of structuring you’d ordinarily do in a show is not necessary. You need just enough structure to indicate the physical situation in which the monologue is taking place. For instance, if the character in your monologue is standing on a ledge about to jump, you’d want to indicate this physically in the simplest and most unobtrusive manner. Using too much structure to set up this situation could easily descend into bad pantomime.
When structuring an audition monologue follow the rule “less is more”. Structure only what is needed in order to make sense of the monologue in the audition environment. Too much structure will inhibit the impact of your characterization.