How Do I Start A Cover Letter?

Firstly I recommend calling the company(unless advised no calls) and asking who the human resources director is for the company or look online at a companies website, be sure to ask their heading (DR./MRS./MISS/MS.) as well as the spelling of the name.  I would not ever use the to whom it may concern it shows a lack of knowledge about the company.  Be sure in the letter to say what your strengths are and what you can bring to the company.  Be confident in your skills, if you aren't and can't seem to find a reason for them to need you, they will also see this.  Good Luck in your job search.