Initial interviews are either solicited by online means (CL, Indeed, etc.). Resumes from interested applicants are always accepted and reviewed to determine merit.
Initial interview - predominately done by phone, to determine professionalism, competence and phone etiquette as much client interaction is required in all positions.
2nd interview - performed by firm administrator, background check and reference verification
3rd/Final interview - performed by principal in the firm, overall firm-culture fit is determined as well as skill level, and communication efficacy.