Make sure you have a thorough understanding of the requirements at the outset of your process.
While assignments vary greatly, the prompt is a place to hone in on the action verbs that will help you understand what you are being asked to write. Look for words like research, synthesized, analyze, argue, present, defend.
Know up front exactly which types of resources your professor would like you to use and how many of each (if specified). If you're not sure, don't be afraid to ask your professor!
Now that you have a clear understanding of you assignment, you can spend time gathering enough background knowledge to begin your research and writing.
Find more at The Purdue Owl Online Writing Lab: Understanding Writing Assignments