When I teach English tenses to French students, I always tell them to forget the French principle of "past", "present", or "future". The clues are quite different in English.
So, I ask them to see the things they want to express as if they were film-makers, and to cast a different light on the events. "What do you want to emphasize?" "What's the message you want to convey?" "Is it still going on at the moment you're speaking?" "How do you picture the next scene?" etc etc...
Do you teach English? Well, I guess you do...