Will (future simple) is used for predictions where the outcome is unknown, sudden decisions, and offers. Be going to is used for plans, intentions, and evident predictions where the outcome is known. The present continuous is used for planned actions at a specific time in the future. The present simple is used for future events scheduled at a specific time like timetables or schedules.

1. FUTURE TENSES
WILL (FUT. SIMPLE) BE GOING TO PRES. CONTIN. PRES. SIMPLE
• Predictions (we • Plans & intentions • Arrangements: • future events at a
don´t know): (an idea for the planned actions at a specific time
We´ll travel future): specific time (your (timetables or
I´m going to meet intention or plan has schedules):
to Mars in 20 years. The plane takes
my friends. been arranged):
• Sudden decisions: land at 11:40.
(but I haven´t I´m meeting
I´m hungry!
phoned them yet) my friends at seven. We leave to
I´ll make a sandwich. We´re having Edimburgh at nine.
• Evident predictions
• Offerings: (something we a birthday party.
-Will you have know):
something to drink? We are going to have
- No thanks, a baby in 2 months.
I won´t have
Look at the sky!
anything.
It´s going to rain
in a few minutes.