[Present Simple] for fixed timetables, schedules and arrangements.
Don't forget it closes at 10.30 on Sundays.
[will] for immediate decisions made at the same time as you speak/write.
I'll call you later.
[will] for something you think, guess or calculate about the future.
Most of the family will probably be there.
[be going to] for a personal intention or arrangement.
We're going to have a barbecue.
[be going to] for predictions you make because of present evidence.
Judging from the grey sky, it's going to rain anyway.
[Present Continuous] for fixed plans or arrangement.
Grolia and I are meeting there at about 8.30.
[Future Continuous] for something that will be in progress during a period of time in
the future.
I'll be working all weekend.
[Future Perfect] for something that will be finished before a time in the future.
Maybe you'll have done your various duties by the end of the evening.