I originally wrote this blog post for  Comic Vine, but it may be useful to some Giant Bomb wiki editors too.  So, just what is a plot summary? I googled "what is a plot summary" and found some great answers.  According to Answers.com here is what a plot summary is:

A plot summary is a description of the story in a novel, film or other piece of storytelling. It is not a review and should not contain the opinions of the author. It should contain all the necessary information about the main characters and the unfolding drama to give a complete impression of the twists and turns in the plot, but without confusing the reader with unnecessary detail. 

A plot summary is not a recap. It should not cover every scene and every moment of a story.... Not only should a summary avoid a scene by scene recap, there's no reason why a plot summary has to cover the events of the story in the order they appear (though it is often useful). The point of a summary is not to reproduce the experience—it's to explain the story. If the original is non-linear or experimental in its structure, the article should state that fact in prose, not through regurgitation of the plot.  In fact, for a confusing story, we should assume that some of our readers will look the story up because they didn't understand it. Just repeating what they saw isn't going to help them!   

While longer descriptions may appear to provide more data to the reader, a more concise summary may in fact be more informative as it highlights the most important elements. By focusing the reader's attention on the larger structures of a plot, without drowning it in trivial detail, a shorter summary can often help the reader to understand a work much better than an overlong one. Excessively detailed plot summaries may also infringe on copyright and fair-use concerns     

• Plot summaries should be in the present tense.     
• Avoid trivial details.
• Plot summaries should summarize; explaining only the most important elements of the story.
• Read what you write out loud -- read it word-for-word like a robot -- before you save it.  
• Write well.