We use will for: future predictions based on what we think or
imagine. I think life will be better in 2100.
* on-the-spot decisions. It's cold. I'll close the door.
We use be going to for:
future predictions based on what we see. Watch
out! You're going to fall.
future plans & intentions. Now that I've got the
money, I'm going to buy a new computer.
We use present continuous for fixed arrangements.
John's leaving tomorrow. He got his ticket.
