Inform actors you wish to cast small parts. Announce this where actors will see or hear it with the appropriate media and details. Ask actors to submit head shots for consideration.
View the submitted head shots with the director and producer to choose a list of possible candidates for the small parts.
Hold preliminary auditions. Ask the selected actors to read a part of the script in front of you, the director and the producer.
Choose the best candidates for the small parts and ask them to come back for a final audition.
Ask the actors to preform scenes with other selected actors in the final audition to decide which actors have the best connection and abilities. Discuss the possible candidates with the director and producer and select an actor for each small part.