Be going to

• Future intentions

• You don't know exactly the hour, place etc

  e.g. One day I am going to try that new Vietamese restaurant.

  She is going to be upset about the mess.

  They are going to sell their house because they want a bigger one.

Present continuous

• Future arrangemets

• You know details like the hour, place etc

  e.g. Tomorrow I am leaving at 6 a.m.

  Jack and Jenny are meeting for lunch today at 2 o'clock.

  She is having a birthday party on Wednesday next week.