Subject pronouns
In spanish you usually drop the subject pronouns. But what if with a verb like estar, where the conjugations of the first person and third person are sometimes the same (estaba for example) . Do you than add the subject pronoun?

Question

Answer

You can use them or not, depending on what you're try to express and the context. 
Ej. 
Ayer estaba en el gimnasio y me encontré a a Juan. Creo estuvo de vacaciones porque estaba muy bronceado.

Answer

Usually, the subject is clear from the context.  When that it not the case, using the subject will make clear who you are talking about.

Answer

Usually it's obvious from the context, but you can use the subject pronoun, if you need to.  Normally you use Ud.