I have a specific question about verbal inflection and how best to explain the correct usage and a general question about verb tenses/conjugation and how best to explain correct usage.
Sometimes explaining these things in a way that helps people to understand can be very difficult. I am a computer programmer mentoring a young woman who is very skilled at programming but speaks very poorly. I would like to do a better job of helping her recognize and correct some of her more glaring mistakes as her poor speech causes others to dismiss her as unintelligent when in fact she is quite bright. Unfortunately for me I started reading at a very young age and totally ignored my teachers when all of this was being discussed in class because correct syntax was already ingrained so I didn't bother learning the rules and terminology. That leaves me at a loss when I need to explain the correct usage to others.
Specific question: How would you go about explaining that to say "He ran the race yesterday" is correct, but to say "He had already ran the race when I called him" is not correct. In other words, the second sentence should be "He had already run the race when I called him."
General question: I've tried correcting younger people who say, for example, "They does their work very well" only to be told "does" is correct because "they" is plural and so the verb has to have an "s". Do you have any suggestions for me in helping to correct these kinds of misunderstandings?