Future Tense

“Will” is used for on-the-spot future decisions or future facts (predictions based on general knowledge or beliefs)

•      Thanks for letting me know.  I’ll call you tonight.
•       OK, in that case I’ll come by tomorrow.
•      I’ll be thirty in a few days time.

“Going to” is used for a prediction or intention based on something you observe, in other words a present fact.

•       She’s going to be a ballerina.
•       He’s going to be a race car driver.
•      That vase is going to fall off the table.

Note that there is sometimes little difference between will and going to. 

•       We’ll run out of money if we are not careful
•     We are going to run out of money if we are not careful.

In these cases, “going to” is often used for cases in which there is outside evidence, while will can be based on our opinion in the lack of evidence.

Present continuous is used for planned future arrangements without a noted length or duration 

·      We’re having our exam this Friday.

•       I’m having dinner with Fred tomorrow night.

Future continuous is used for something that (a) has an ongoing duration in the future or (b) will be a naturally occurring thing.

•       Friday at this time we will be having our exam. 
•       Don’t call tomorrow at 8:00 PM as we will be having dinner.
•      In ten minutes class will be ending.

Timetables and schedules use present simple:

•      The plane leaves at 8:45 PM.

Shall is only used in very rare cases, specifically when we are asking a very polite question in first person:

•      Shall we have our dessert now?