Hi!
After a year of business teaching and looking for students online I came back here again and read your post.
I have been teaching English conversation practice for more than 3 years but that is not enough of course.
When your student talk about a certain topic he can combine those 3 tenses accordingly. If he is talking about the action done in the past then he can use thepast tense and talk about the present action then he can shift to the present tense ; When I was a teen-ager, I prefer to.. I planned to ..in the future...currently I am...
I hope this helps..

Aubrey