When writing essays for class, it's important to get your scope down to a sensible focus.
Minds don't normally work the same way that an essay should be written, so you'll need to pay conscious attention during the process.
Wide Scope During brainstorming, it's not unusual to end up with too wide a scope.
Since you'd like to have everything you will need for the piece, putting down all sorts of research, quotes and findings is appropriate.
Trimming The Fat The best way to cut down on a scope this wide is to begin eliminating portions of the notes that don't have anything to do with your main thesis.
If it supports or contradicts (hey, you need a counter-argument, too) your major statement, keep it; if it doesn't, kick it.
Your Outline The outlining process represents the best time to narrow the scope of your essay, because the shape of your piece usually materializes at this point.
While you can also do it during the actual writing, it's not the most efficient use of time, extending the process unnecessarily.
Editing Just as you work on your writing's overall quality with a grammar software during editing, you should also consciously note your scope at this time.
When you read through the piece, watch out for content that may be straying from the main idea and alter it accordingly.
Remember that when you are narrowing your scope, then, you can be able to express to your readers what you are trying to imply in your essay.