The audition process is fascinating for a number of reasons. As a production team member, you’ve probably read the script and have an idea of what you’re looking for in some or most of the character performances. Once you bring actors into the fold however, it’s like laying a wild card down on the table. The auditioning actor has an idea for the character that may be at complete odds to what you have in mind. Don’t be discouraged or frustrated - few people get it right on the first try. It’s called an audition “process” for a reason!
Contrary to popular belief, the audition is not only about testing a person’s acting ability, or about matching an actor to a character. By bringing on actors and cast, you’re expanding your production team. Especially if you’re a producer or director, casting agent, or other decision-maker, you are in certain ways bringing on a colleague. You may be working with this person for a number of days, weeks, or months. It’s important that the actor be able to communicate effectively with the director and other members of the team. Having a talented actor in a lead role might bring the film clout, but if they don’t work as part of a team or aren’t manageable, it may cause others to lose morale, and lower your overall production value.
When the actor comes in to read, unless you’re providing the material “cold” (and I do not recommend this), they will likely have prepared a performance. Chances are, it won’t be exactly right. This is where you discover their ability to act, and their ability to communicate. Have the actor read the scene more than once, and ask for adjustments in the performance. The object here is not only to see if you can bring the actor closer to your vision of how the scene should play out, but also to see how they take direction. Did they understand the adjustment you asked for, or did they take it the wrong way? Don’t repeat the scene ad infinitum. Two or three read-throughs should give you a good idea of what the actor is bringing to the scene, and your ability to guide their performance.
Sometimes you will audition an actor who is a dead ringer for the role, who reads every line exactly the way the director hears it. In this case, it’s still a good idea to ask for a few adjustments. Even though they read the scene the way you envisioned it, you still need to be sure the communication works. Also, it’s an opportunity to explore the actor’s range, and to see what else they’re capable of with the scene. Ask them to bring different elements to the psyche of the character and see how that changes their performance. Especially at the audition, actors want to act. They want to show you what they’re capable of! So give them a few suggestions. That’s what they’re here for!
A final thought: Hopefully you have your pick of great actors for your film, and your only problem is narrowing down who you want at the callback. However if you find yourself with a cast you’re unsure of, keep an open mind. Sometimes an actor will find a performance you wouldn’t have thought of otherwise. Working with actors is about communication, patience, and creativity - and if you’ve chosen a good teammate, you’ll overcome any obstacle.