#3 -- Telling what the company can do for you rather than what you can do for the company.

The employer wants workers who can solve problems, make money, and be productive. Making you happy is fairly far down on the list of the employer's priorities. You always need to focus on telling the employer how you can contribute to the organization's success.

Follow this link for excerpts from letters that make the mistake of focusing on what the employer can do for the jobseeker.