Do not start writing the resume until you have any idea about the employer. Also, you should remember this important point: you need to show the employers what you can benefit them but not what you may benefit from them. The perfect resume must focus on the strength in necessary experience and skills that the employer may require from you. You will score more point with your knowledge about the employers and understanding of what they expect from you.
Do not miss these important details and do not forget to start your resume professionally with clear address of the company and even, the name of the responsible person. The employer will understand that you have researched carefully about them and correct your resume before sending to them, and, you have gained a good score then!