To prepare yourselves for making the best product, you have to ask yourself 'what makes a good story?'. Think about your favourite piece of art/entertainment (written story, film, game, etc.) and think about what makes it good.
Writing
Describe a few of your favourites (mentioned above) using elements from the reader such as plot diagram, characters, setting, themes, genres, conflicts, etc. Discuss what elements your favourites have in common, and what about those elements make these stories appealing to you.
Speaking
Find a partner and compare your favourite stories (in the broadest sense of the word). Think of what makes these works your favourites and describe them to your partner. What do your favourites have in common? What does a good story entail?