Failing to organize and prepare your thoughts before starting your first draft might be the most common (and harmful) mistake students make. From elementary school students to professional writers, everyone benefits from approaching their writing with a plan in hand.
As you organize your thoughts, continue your research process and decide where new information fits into your plan. Often, by grabbing a few articles to begin with, you can start making decisions on what goes where. After you've finished your initial research, your later research should fall into the same categories you established early on.