Make your resume and resume differ from those of other candidates. As such, you should never start your resume with such general salutations as dear sir, or dear sir. Normally, when a company posts publicly a recruitment ad, it will surely address the name, address and contact number so as the resumes may be sent to correct address.
Find out about the employers: Do not let your resume or resume in disorder or write a resume or resume in a certain available form. Resume and resume are one way to show off your personality and make the best explanation to the employers question why they are impressed at you but not at other candidates.