Everything has a form. In writing, the goal is to find a form that suits your material and purpose. You may sense a clear pattern emerging early in your writing process, or you may try out a few promising designs.
Sensing how your emerging ideas fit into an overall design, you can move forward more confidently than if you had to keep spinning out words with no sense of where they might lead.
Either way, strong organization helps you and your reader. It offers you guidance and direction as you explore your ideas. Sensing how your emerging ideas fit into an overall design, you can move forward more confidently than if you had to keep spinning out words with no sense of where they might lead. Also, effective organization helps readers see how various parts of your paper relate to each other and to your unifying purpose.
If readers sense that you're in control, that you know where you're going and how you'll get there, they'll more likely come along than if you appear to lack direction and purpose.
The following discussion shows the general concepts that underlie most organizational techniques and looks at some specific patterns you can use in your own writing. Notice, also, that the Paradigm sections on Informal Essays, Thesis/Support Essays, Exploratory Essays, and Argumentative Essays contain advice on organization.