• The majority of verbs in the past use avere, including the verb avere itself. The past participle endings stay the same:

  Ho visitato la chiesa	I visited the church
  Abbiamo visitato il museo	We visited the museum
  Ho avuto un incidente	I had an accident

   

• Essere is used with stare, 'to stay' or 'to be', and with the verb essere itself:

  Sono stato felice di vederti	I was happy to see you
  Sono stato a Roma per due giorni	I stayed in Rome for two days