You may think this is a no-brainer. Well, many candidates miss the mark by starting with a generic opening paragraph.  Present yourself as a worthy candidate by stating the position to which you are applying (or department). Support  this with how you meet the basic requirements 

in terms of education and experience.

Based on what you have learned about the company and the job opportunity, identify your top skills.  Prove those skills by citing a top accomplishment. Include the scope of your responsibility to drive home the trust your former employers had in 

you. Brainstorm to uncover these valuable selling points.

The last paragraph is where you wrap it up by identifying next steps. In most cases your best strategy is to commit to making a follow-up call and fulfilling on that commitment. Offer to provide additional information as needed and always thank the reader for considering you for the position.