I was blogging recently about my course subtitled Narrative Devices (10 March 2011) and think it could be useful to go on. One Learning Outcome is Define verb tenses and their effect on narrative. Sounds so basic, yet I really only arrived at it because I was forced to break down creative writing into specific craft skills; turns out to make for some good exercises.
I invented two Criteria for Assessment.
1) Recognise present, past and past-perfect verb usage in published or own writing.
2) Evaluate strengths and weaknesses of different verb tenses in narrative effect.
Sneakiest way to get into this is to set an exercise, probably starting with a stimulus of listing or even a given list of words to choose from, where you ask students to write a paragraph or two about something (place, object, pet, person, event...). Or it could just start with 'I remember...' and go on.
Why is this sneaky? Because you want them naturally and unselfconciously to write in past tense. This is your (their) raw material. And now you talk a bit about present tense, maybe read out an example, and ask the students to transmute (or maybe we should say timeshift) their own piece into present tense.
They set to it... and then they start to say it is hard to do! Urge them to soldier on. Also some 'ask permission' to leave things out or change things because it won't work otherwise. Aha! Now they are seeing the craft differences in the two modes. Of course it's okay.
Then read out and share and comment and discuss. Good to prepare a handout of excerpts from published works in both past and present tenses to read out to further support the discussion. There's no right answer, it's just... how does it feel? what does it convey? is this the effect you want? have you considered the effect?
A variant or addition is to have students transcribe (transmute? timeshift?) the published excerpts into the other mode; again -- to sense the effect on the reader. Effect on the writer might be considered too -- some people love to write in present tense, some hate it, some can only flow in classic past-tense storytelling, some feel paralyzed by it.
Hmm, all this and I didn't even get to past-perfect, otherwise known as the had-hads.