FUTURO CON "GOING TO"
Para formar el futuro con "going to" necesitamos usar el presente simple del verbo "to be" (ser, estar) seguido de "going to" y luego otro verbo.

Ejemplo

He is going to study English at university.
Él va a estudiar inglés en la universidad
We are going to go to the theatre next month.
Vamos a ir al teatro al mes que viene

Para la forma negativa usamos "not" (no) detrás del verbo "to be" (ser, estar).

Ejemplo

She is not (isn't) going to buy that car.
Ella no va a comprar ese coche
They are not (aren't) going to send the parcel back.
No van a enviar de vuelta el paquete

Para la forma interrogativa colocamos el verbo "to be" (ser, estar) delante de la persona.

Ejemplo

Are you going to use the computer this afternoon?
¿Vas a utilizar el ordenador esta tarde?
Is she going to go to South Africa soon?
¿Va a ir (ella) a Sudáfrica pronto?

ALGUNOS USOS GENERALES

Usamos el futuro con "going to" para expresar planes de futuro. Normalmente nos referimos con el futuro con "going to" a un futuro cercano.

Ejemplo

I am going to study for my exams.
Voy a estudiar para mis exámenes
I am not going to go by bus, I am going to go by car.
No voy a ir en autobús, voy a ir en coche
Are we going to have lunch today?
¿Vamos a almorzar hoy?
He isn't going to the dentist today at 4, he is going to go tomorrow.
Él no va a ir al dentista hoy a las 4, va a ir mañana

El futuro con "going to" se usa para expresar intenciones o acciones a las que el hablante ha accedido o ha prometido llevar a cabo.

Ejemplo

I am going to buy a new computer.
Voy a comprar un ordenador nuevo
We are going to help you with your verbs.
Vamos a ayudarte con los verbos
They are going to cook lunch for us.
Van a cocinar el almuerzo para nosotros

Cuando no estamos muy seguros de lo que va a suceder en el futuro, también usamos el futuro con "going to" para expresar nuestros pensamientos o predicciones.

Ejemplo

We think they are going to go abroad.
Creemos que se van a ir al extranjero
They have the feeling their company is going to expand.
Tienen la sensación de que su empresa se va a expandir

Vamos a conjugar un verbo a modo de ejemplo. Vamos a coger el verbo "to study" (estudiar).

Afirmativa

Negativa

Interrogativa

I am going to study am not going to study Am I going to study?
You are going to study aren't going to study Are you going to study?
He is going to study isn't going to study Is he going to study?
She is going to study isn't going to study Is she going to study?
It is going to study isn't going to study Is it going to study?
We are going to study aren't going to study are we going to study?
You (all) are going to study aren't going to study are you going to study?
They are going to study aren't going to study are they going to study?

http://www.helloworld.com.es/Spanish/quick%20reference/verbs/english/futurewith.htm