Reserve a rehearsal room at a studio or find a similar space where you can have actors come in to read for a part in your web series.
Place ads in classified sections of local papers or online classified websites. Describe in 2 or 3 sentences the personality and physical type of each character you are looking for. Put a synopsis of your story at the top of your ad. Tell the reader when the audition will occur and when you plan to shoot.
Choose sections of the script that best represent a deep look into each character's personality. Use a scene where a character has an emotional turning point, if available.
Send actors the scenes they will be auditioning with at least 2 days before the audition occurs.
Record the auditions and review the performances with your director and producer. Choose actors who most embody your characters emotionally and physically.