A key first step in creating your resume is gathering information. Some facts will be more obvious, like companies you've worked for or courses you've taken. Assembling this basic information is a great way to get started, especially if you tend to procrastinate!
But for a focused resume, you need to dig deeper to determine what you're looking for, what employers are looking for, and how it all fits together.
Your overall objective is to match your goals and qualifications to employers' needs. This is what will ultimately win you the interview.