I'm (I am) going to take my holidays in August. 

I'm (I am) not going to take a holiday this year.    

Are you going to take a holiday?

He's (he is) going to watch TV this evening.

He isn't (is not) going to watch TV this evening.

Is he going to watch TV this evening?

You know that I am going to buy a new car, don't you?

We use going to for a future action that has been decided before the time of speaking.

Look! You are going to drop your books.

We use going to if we see (and are sure) that the action will happen.