Hi Doug: You may omit the pronoun in most cases (there won't be any confusion as the conjugation in this case is unique). However, in some situations, when you need to emphasize or make a contrast, you may use it: Person 1: Tengo hambre. Person 2: Yo también. Person 1: Vamos al parque. Person 2: No, (yo) tengo hambre; vamos a comer primero.

It´s right what the other answers say, it depends on the context. Taking your example: A: Tengo hambre, ¿vamos a comer? B: YO no tengo mucha hambre, pero si quieres vamos. Usually, you add YO when you want to emphasize that you are the subject.

In most of the cases you may omit it as Andres said earlier, but sometimes you HAVE to use it as for example in: A: ¿Quién va a la fiesta? B: YO voy (so in this case you can omit the verb but not the subject) or in: A: Carla hizo todo el trabajo pendiente. B: No, YO hice todo el trabajo pendiente./YO lo hice.

You must avoid to repeat the pronom for example in this case: "Yo me llamo Doug. [Yo] nací en EEUU. [Yo ] tengo 2 hermanos. [Yo] practico mucho deporte. etc"