How do I explain the difference between Will and Going to to a group of Brazilian learners?
I don't think Brazilians need a special explanation. Emotion: wink

"Will" implies an uncertain future, a desire. "Going to" is a closer one, much likely to happen. Compare:

A: What will you do when you finish high school?
B: I'm not sure yet. I think I will go to college to study Engineering.
A: Just like your brother?
B: Well, no. He's going to college this year, but he's going to study Economics.
A: Oh, I see.

Also, when you talk about an inmediate or expected (confirmed?) future you can use the ING form:

John's getting married tomorrow.
I'm going to the movies tonight.
Jane's having a baby in November.

Hope this helps! Emotion: smile
I´ve read the comments about the difference between will and going to, and since I´m a English teacher in training, it has really helped me a lot. Many thanks!
It seems to me that it would be similar to the difference in Portuguese, wouldn't it?

In any case, here's the shortest possible explanation:

going to is hot; will ('ll) is cold.

Stop playing in traffic!!! You're going to get killed!!!
I can't stand him. Maybe someday he'll get killed in traffic.

See Will for more details.

thank you this helped
Great job, thanks a lot!
can you explain me please
Got it