This is an article I think fans of writing 'action' scenes should definitely not miss. She touches on so many things that are important, including purpose of fight scenes, content, perspective ...all the things we so often see done poorly by beginning writers who want to create 'excitement.' This is a woman who has personal experience in martial arts, and is a published author. Good stuff. http://www.writersdigest.com/editor-blogs/guide-to-literary-agents/blow-by-blow-writing-action-and-fight-scenes?et_mid=791437&rid=239329351
I disagree slightly with the article. It doesn't have to be crucial, just purposeful enough How much of the story is truly crucial? How do you even decide that? When is the thing changed enough to be consider too different? It's rather irrelevant to say "crucial" unless you're talking something in the story that is part of the basic premise and plot outline. Other than that, I think it's usually impossible to say something is crucial, only if it's damagingly unnecessary.