The personal 'a' is used when the direct object of the verb is a 'identified' person,
e.g. Espero a Rosaura - I'm waiting for Rosaura; Detuvieron al ladrón - They arrested the thief
It is not used before an 'unspecified' person; compare Buscamos un profesor de español - We are looking for a Spanish teacher and Vi a mi profesor de español - I saw my Spanish teacher.
It can be used with animals, when the animal is thought of as a 'person', e.g. Voy a pasear al perro - I'm going to walk the dog.