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.
Almost people who tend to seek a job understand that resume is the decisive factor to whether you can make it to the interview round or not. Moreover, do not forget that resume and resume is two sides of the one which show your outstanding capability.