Review pages 4-7 of the Evaluating Wikipedia brochure. This will give you a good, brief overview of what to look for in other articles, and what other people will look for in your own.
Evaluate an existing Wikipedia article related to the class, and leave suggestions for improving it on the article's talk page.
A few questions to consider (don't feel limited to these):
Is each fact referenced with an appropriate, reliable reference?
Is everything in the article relevant to the article topic? Is there anything that distracted you?
Is the article neutral? Are there any claims, or frames, that appear heavily biased toward a particular position?
Where does the information come from? Are these neutral sources? If biased, is that bias noted?
Are there viewpoints that are overrepresented, or underrepresented?
Check a few citations. Do the links work? Is there any close paraphrasing or plagiarism in the article?
Is any information out of date? Is anything missing that could be added?