First, you should have a significant thesis, some meaningful point that you want to make in the paper. The more thoughtful, profound, controversial or insightful, the better. The thesis should be clear and specific.
Trifles is a play about men and women and their relationships.
Trifles uses a lot of stage action to get its point across. Susan Glaspell skillfully manipulates her characters and setting to dramatize a conflict between the way men and women view the world. Then, you should always acknowledge weaknesses or questionable areas in your thesis. Don't write as though your opinion is the only valid one. Question your assumptions.