For too long the preterite and imperfect tenses were taught in this manner:
1. Teach how to conjugate the two tenses and all the irregularities.
2. Teach the rules for applying the two past tenses.
3. Teach the signal words for each tense (always, yesterday, etc.).
4. Have students complete cloze exercises to practice choosing between the tenses within a context.
The problem with this is that a story can only be accurately told from the narrator's perspective. Only the narrator knows his intent when telling the story, so when we ask our students to complete someone else's story, they have a very hard time knowing what the narrator intended to say. Did he mean the child used to play with Barbies or that the child played with Barbies one day after school. Without signal words, our students really don't know what to put in the blanks.
Since the real use for the two past tenses is to tell your own stories, we have to coach our students how to make that tense decision while telling one. One of the things I try to do when I teach this concept is to convey to my students how my own Gringo brain works when I tell my own story. Last year I finally came up with something to hand out to my students to help them make those decisions.
Another strategy I employ to help my students' Gringo brains adopt this new skill is to start with very condensed versions of their own stories.
Here's a couple examples activities I use as an introduction to storytelling in Spanish:
This would be the very first storytelling activity I would have the students do. I might even do this several times but with a different context each time. My rationale is that Gringos can't tell a long story successfully in Spanish if they can't handle one sentence in Spanish, so the One Sentence Story was invented to start there!
First, ask students to take out a sheet of paper and fold it fan style into 4 sections, then have them label the sections with the numbers, but leaving room to write their stories.
Provide a topic for them to write about.
Now, ask them to write a one sentence story about that topic in the #1 section of their paper. This works best if the story is something personal to them. Instruct them to bring it to you when they are done for you to help them edit it.
After editing their one sentence stories, now instruct them to move to section #3 and rewrite the story, but add two new sentences to the story to bring in more of the stories events. Again, instruct them to bring the completed 3 sentence story to you for editing help when they are done.
When the editing is complete for section #3, instruct them to move to section #5 and rewrite their 3 sentence story and add two more new sentences adding further events or description to it. When they have done that, instruct them to bring it to you again for your last effort to help them edit their story.
The last step in the process is to direct the to section #8 and have them finish the story by adding 3 final sentences to either provide background, description or important events in the story that would make the story complete. After this step, instruct your students to turn it in. It is now ready your assessment, peer assessment, peer reading and commentary or any type of evaulation.
Option: Have your students write new sentences in a new color each time they add to the story so the new sentences stand out and you don't have to edit the whole story each time.