Step 1

We use the personal a with people and pets.

María visitó a su abuela.
      Maria visited her grandmother.
Conocí a Miguel en mil novecientos ochenta y
       cinco.
      I met Miguel in 1985.
Yo invité a María a ir a la fiesta.
      I invited Maria to go to the party.
¿Quién llamó a la policía?
      Who called the police?
Ellos fueron a visitar a su tía.
      They went to visit their aunt.

Exceptions:
We don't use the personal a with tener, necesitar, and haber.

Tuve dos hijos.
      I had two children.
Necesité un médico.
      I needed a doctor.
En mi familia hubo seis personas.
      In my family there were six people.