Going to

Para os planos futuros usamos (For future plans we use):

am / are / is going to + verb.

I am going to watch The Big Bang Theory this weekend.

Para futuros próximos usamos (For future arrangements we use):

The present continuous am / are / is + verb + ing.

I am watching The Big Bang Theory with my sisters.

Affirmative

Subject + verb to be + going to + infinitive main verb without to. (Sujeito + Verbo to be + Going to + Infinitivo do verbo principal sem to).

Negative

Subject + verb to be + not + going to + infinitive main verb without to. (Sujeito + Verbo to be + Not + Going to + Infinitivo do verbo principal sem to).

Interrogative

verb to be + Subject + going to + infinitive main verb without to. (Verbo to be + Sujeito + Going to + Infinitivo do verbo principal sem to).

Will ou Going to, quando usar.

Will geralmente é usado quando expressão indica incerteza.

I will (probably) go to Rio in December.

I (guess) I will leave this apartment soon.

(Maybe) we will not be here tomorrow.

Going to você usa quando está decidido, praticamente certo (sem dúvidas) do que vai ser feito.

I'm going to visit my mother next week.