Got plans or predictions?
-> Going to + infinitiveEX: I am going to London next week.
He is going to hurt himself on that roof.
Prediction? Future fact? A promise? An offer? -> Will/won't + infinitive
EX: I will get a 10 on my test next time.
I will help you with that.
Is something going to happen in the near future? -> Present continuous
EX: I am seeing Bill later today.
Is something already planned or set in a schedule? -> Present Simple
EX: The bus leaves in 5 minutes.