Oh my God! Look at the clouds! It is going to rain soon! Let's get inside!

• "Be going to" is used here because the clouds indicate a future event based on current evidence.

I promise you, mom, I will be a good child.

• "Future Simple" is used to make a promise or commitment.

What are your plans for tonight? - Well, I am going to have dinner with my parents and my boyfriend, Bryan, and then I think we are going to go for a ride.

• "Be going to" is used to describe planned activities.

Stop teasing my hair or I will not get you a lollipop.

• "Future Simple" is used to express a consequence of an action.

So, Gerald and Scarlet are going to redecorate their living room next week.

• "Be going to" is used to describe a planned future action.

Sebastian's afraid he will miss the deadline. He thinks he will fail the class.

• "Future Simple" is used for expressing concerns or predictions about the future.

Put a jacket on you or you will catch a cold!

• "Future Simple" is used to indicate a consequence of an action.

Our plans for this evening are awesome! We are going to go to Selma's party and then probably me and George, are going to have some private time!

• "Be going to" is used to describe planned activities.

Well, what would you like to do for a living? I really haven't thought about it. I guess I will learn Arabic and Russian.

• "Future Simple" is used to describe a future intention or choice that hasn't been planned in detail yet.

How dare you lying to me? I will not trust you again!

• "Future Simple" is used to express a strong reaction or decision based on a current situation.

Someday, I will move with my parents in Canada.

• "Future Simple" is used to describe a future intention or plan that is not yet immediate.

-Here's the menu, sir. What would you like to have?

• "Future Simple" or polite "would like" is used to ask for a choice or preference.

-Look at this dress! I am going to buy it!

• "Be going to" is used to express a strong intention to purchase the dress.

I will have pasta with meat. Thank you!

• "Future Simple" is used to state what you will choose or do in the future.