If you are just beginning with your resume writing perhaps to start you need to do some research. Some advise that you should justy just start writing by listing strengths, how you can contribute to a company, projects you were you involved in, your past responsibilities and duties etc. Yes you will have to get to those as part of the process however when you do write them they need to be written with reference to a potential employer's requirements. To my way of thinking to start it is best to read and take notes before you commence the 'formal' writing process.
Look at the advice you can find on the web and review newspaper job ads. With your preparations keep in mind that your resume is your personal marketing tool and good marketing is target marketing. Your resume will, when you put it on paper, need to succinctly describe what you have to offer and it must in its final form be individualsed so that it is based on what the employer has stated as being required in his/her advertisement.