To tell the story of a work of literature or a historical sequence, most writers use the "historical present"—that is, they tell of the events as if they were happening in the present.
1. At the end of the movie Love Story, Jennifer dies a tragic death. [Historical present correctly used. It is permissible to use either the historical present or the simple past tense in such cases, but whichever one you use, use it consistently.]
Frequently, however, errors of tense are due to standards that vary across disciplines. Check with your professors to find out what tenses their departments prefer.
For more information on writing for specific disciplines, refer to Organizing your Paper in this handbook.
For more information on tenses, see Verb Tense, available online at the Writing Center home page and in hard copy at the Writing Center, and Strunk and White, The Elements of Style (Rule 21).